Given a question and a context passage, generate the answer having the word or phrase from the context passage. Here, the answer should be a shortest continous span from the passage.
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Question: Context: A cell is the smallest structural and functional unit of an organism. Some organisms, like bacteria, consist of only one cell. Big organisms, like humans, consist of trillions of cells. Compare a human to a banana. On the outside, they look very different, but if you look close enough youll see that their cells are actually very similar. Most cells are so small that you cannot see them without the help of a microscope. It was not until 1665 that English scientist Robert Hooke invented a basic light microscope and observed cells for the first time, by looking at a piece of cork. You may use light microscopes in the classroom. You can use a light microscope to see cells ( Figure 1.1). But many structures in the cell are too small to see with a light microscope. So, what do you do if you want to see the tiny structures inside of cells? In the 1950s, scientists developed more powerful microscopes. A light microscope sends a beam of light through a specimen, or the object you are studying. A more powerful microscope, called an electron microscope, passes a beam of electrons through the specimen. Sending electrons through a cell allows us to see its smallest parts, even the parts inside the cell ( Figure 1.2). Without electron microscopes, we would not know what the inside of a cell looked like. The outline of onion cells are visible under a light microscope. In 1858, after using microscopes much better than Hookes first microscope, Rudolf Virchow developed the hypoth- esis that cells only come from other cells. For example, bacteria, which are single-celled organisms, divide in half (after they grow some) to make new bacteria. In the same way, your body makes new cells by dividing the cells you already have. In all cases, cells only come from cells that have existed before. This idea led to the development of one of the most important theories in biology, the cell theory. Cell theory states that: 1. All organisms are composed of cells. 2. Cells are alive and the basic living units of organization in all organisms. 3. All cells come from other cells. As with other scientific theories, many hundreds, if not thousands, of experiments support the cell theory. Since Virchow created the theory, no evidence has ever been identified to contradict it. Although cells share many of the same features and structures, they also can be very different ( Figure 1.3). Each cell in your body is designed for a specific task. In other words, the cells function is partly based on the cells structure. For example: Red blood cells are shaped with a pocket that traps oxygen and brings it to other body cells. Nerve cells are long and stringy in order to form a line of communication with other nerve cells, like a wire. Because of this shape, they can quickly send signals, such as the feeling of touching a hot stove, to your brain. Skin cells are flat and fit tightly together to protect your body. As you can see, cells are shaped in ways that help them do their jobs. Multicellular (many-celled) organisms have many types of specialized cells in their bodies. Red blood cells (left) are specialized to carry oxygen in the blood. Neurons (cen- ter ) are shaped to conduct electrical im- pulses to many other nerve cells. These epidermal cells (right) make up the skin of plants. Note how the cells fit tightly together. While cells are the basic units of an organism, groups of cells can perform a job together. These cells are called specialized because they have a special job. Specialized cells can be organized into tissues. For example, your liver cells are organized into liver tissue. Your liver tissue is further organized into an organ, your liver. Organs are formed from two or more specialized tissues working together to perform a job. All organs, from your heart to your liver, are made up of an organized group of tissues. These organs are part of a larger system, the organ systems. For example, your brain works 
 Question: when were cells observed for the first time?

Answer: 1665


Question: Context: The movie opens with the Barden Bellas about to perform at the ICCA championships. One of them, Chloe (Brittany Snow) is running late to the start of the performance. When she arrives she is reprimanded by the older Bellas. As they are about to perform, Aubrey (Anna Camp) tries to assure them she'll do a good job, but is shot down. The group sings 'The Sign'.. and all is going well, until the very end when Aubrey has a solo, and projectile vomits all over the stage and front rows of the audience.Cut to the start of a new year at Barden University, and freshman Beca (Anna Kendrick) is arriving by taxi. While she is receiving directions and her Rape Whistle, a car passes her by, and another student, Jesse (Skylar Austin) is singing along to the radio, and catches her attention.Beca finds her new dorm room, and meets her roommate Kimmy-Jin, who is hostile and unfriendly. Beca's dad, a professor at Barden then arrives, and asks her how she got there. It is revealed that Beca's parents have split up as she refers to her dad's new wife as her 'step monster', and seems very reluctant to be attending College. Beca's dad tries to encourage her to enjoy it, but Beca escapes to the Activities fair.In another dorm room, Jesse is meeting his roommate Benji (Ben Platt), who is into Star Wars and magic.At the Activities fair, we are introduced to the Trebles - one of the Campus singing groups, all male, who are talented and have a high opinion of themselves, especially Bumper (Adam Devine) the lead singer. Jesse and Benji approach the Trebles, as Benji is desperate to join, but Bumper is not impressed with his enthusiasm.Across the campus, the Bellas are now down to just 2 members - Aubrey and Chloe, who are trying to recruit new ones. Due to their disastrous performance at the last Championships, they are not having much luck, and are even ridiculed by 'Baloney Barb' who has tried out for them previously. They are then approached by Fat Amy (Rebel Wilson), an outgoing and quirky student from Tasmania who doesn't hesitate to demonstrate her singing and dancing abilities. They then meet Beca, who quickly rebuffs their offer to audition, saying it is lame, which immediately puts Aubrey offside.Instead of being interested in joining any of the singing groups, Beca has much more of an interest in remixing music on her laptop. She gets a job at the campus radio station, and much to her dismay, so does Jesse.Her dad pays her a visit in her dorm, and gives her an ultimatum - if she makes an effort and joins a group at College , but still doesn't like it by the end of the year, she can quit and follow her true dream of becoming a DJ, and he will help her... but he wants her to really make an effort.As Beca goes into the communal showers singing to herself, Chloe happens to be in the showers as well, and confronts Beca in her shower stall , insisting that she try out for the Bellas. Although Beca is mortified, she sings along with Chloe to 'Titanium'.Finally the auditions are on, and Jesse, Benji and Fat Amy are among the hopefuls trying out, auditioning to 'Since you've been gone'. Beca comes late, and hasn't prepared the audition song, but auditions with 'Cups (miss me when I'm gone)', and Chloe and Jesse are impressed, while Aubrey is unsure. We then see the initiation of the new Bellas including Beca, Fat Amy, Stacie (Alexis Knapp), Cynthia-Rose (Esther Dean) and the very softly spoken Lilly (Hana Mae Lee). They all swear an oath and drink the 'blood of the Bellas who came before them' (wine). Cut to the initiation of the new Trebles.. Jesse has made it, but Benji has not. That night, there is Aca-initiation where all the groups 
 Question: Who provides an impromptu back-up of one of her favorite songs into the "traditional" song?

Answer: chloe


Question: Context: Friction is a force that opposes motion between two surfaces that are touching. Friction can work for or against us. For example, putting sand on an icy sidewalk increases friction so you are less likely to slip. On the other hand, too much friction between moving parts in a car engine can cause the parts to wear out. Other examples of friction are illustrated in Figure 13.7. You can see an animation showing how friction opposes motion at this URL: [Link] Friction occurs because no surface is perfectly smooth. Even surfaces that look smooth to the unaided eye appear rough or bumpy when viewed under a microscope. Look at the metal surfaces in Figure 13.8. The metal foil is so smooth that it is shiny. However, when highly magnified, the surface of metal appears to be very bumpy. All those mountains and valleys catch and grab the mountains and valleys of any other surface that contacts the metal. This creates friction. Rougher surfaces have more friction between them than smoother surfaces. Thats why we put sand on icy sidewalks and roads. The blades of skates are much smoother than the soles of shoes. Thats why you cant slide as far across ice with shoes as you can with skates (see Figure 13.9). The rougher surface of shoes causes more friction and slows you down. Heavier objects also have more friction because they press together with greater force. Did you ever try to push boxes or furniture across the floor? Its harder to overcome friction between heavier objects and the floor than it is between lighter objects and the floor. You know that friction produces heat. Thats why rubbing your hands together makes them warmer. But do you know why the rubbing produces heat? Friction causes the molecules on rubbing surfaces to move faster, so they have more heat energy. Heat from friction can be useful. It not only warms your hands. It also lets you light a match (see Figure 13.10). On the other hand, heat from friction can be a problem inside a car engine. It can cause the car to overheat. To reduce friction, oil is added to the engine. Oil coats the surfaces of moving parts and makes them slippery so there is less friction. There are different ways you could move heavy boxes. You could pick them up and carry them. You could slide them across the floor. Or you could put them on a dolly like the one in Figure 13.11 and roll them across the floor. This example illustrates three types of friction: static friction, sliding friction, and rolling friction. Another type of friction is fluid friction. All four types of friction are described below. In each type, friction works opposite the direction of the force applied to a move an object. You can see a video demonstration of the different types of friction at this URL: (1:07). Static friction acts on objects when they are resting on a surface. For example, if you are walking on a sidewalk, there is static friction between your shoes and the concrete each time you put down your foot (see Figure 13.12). Without this static friction, your feet would slip out from under you, making it difficult to walk. Static friction also allows you to sit in a chair without sliding to the floor. Can you think of other examples of static friction? Sliding friction is friction that acts on objects when they are sliding over a surface. Sliding friction is weaker than static friction. Thats why its easier to slide a piece of furniture over the floor after you start it moving than it is to get it moving in the first place. Sliding friction can be useful. For example, you use sliding friction when you write with a pencil and when you put on your bikes brakes. Rolling friction is friction that acts on objects when they are rolling over a surface. Rolling friction is much weaker than sliding friction or static friction. This explains why it is much easier to move boxes on a wheeled dolly than by carrying or sliding them. It also explains why most forms of ground transportation use wheels, including cars, 4-wheelers, bicycles, roller 
 Question: force that opposes motion between any two surfaces

Answer:
friction