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.

[EX Q]: Context: Cells were first discovered in the mid-1600s. The cell theory came about some 200 years later. You can see a re- enactment of some of the discoveries that led to the cell theory in this video: MEDIA Click image to the left or use the URL below. URL: British scientist Robert Hooke first discovered cells in 1665. He was one of the earliest scientists to study living things under a microscope. He saw that cork was divided into many tiny compartments, like little rooms. (Do the cells in Figure 3.1 look like little rooms to you too?) Hooke called these little rooms cells. Cork comes from trees, so what Hooke observed was dead plant cells. In the late 1600s, Dutch scientist Anton van Leeuwenhoek made more powerful microscopes. He used them to observe cells of other organisms. For example, he saw human blood cells and bacterial cells. Over the next century, microscopes were improved and more cells were observed. By the early 1800s, scientists had seen cells in many different types of organisms. Every organism that was examined was found to consist of cells. From all these observations, German scientists Theodor Schwann and Matthias Schleiden drew two major conclusions about cells. They concluded that: cells are alive. all living things are made of cells. Around 1850, a German doctor named Rudolf Virchow was observing living cells under a microscope. As he was watching, one of the cells happened to divide. Figure 3.2 shows a cell dividing, like the cell observed by Virchow. This was an aha moment for Virchow. He realized that living cells produce new cells by dividing. This was evidence that cells arise from other cells. The work of Schwann, Schleiden, and Virchow led to the cell theory. This is one of the most important theories in life science. The cell theory can be summed up as follows: All organisms consist of one or more cells. Cells are alive and the site of all life processes. All cells come from pre-existing cells. All cells have certain parts in common. These parts include the cell membrane, cytoplasm, DNA, and ribosomes. The cell membrane is a thin coat of phospholipids that surrounds the cell. Its like the skin of the cell. It forms a physical boundary between the contents of the cell and the environment outside the cell. It also controls what enters and leaves the cell. The cell membrane is sometimes called the plasma membrane. Cytoplasm is the material inside the cell membrane. It includes a watery substance called cytosol. Besides water, cytosol contains enzymes and other substances. Cytoplasm also includes other cell structures suspended in the cytosol. DNA is a nucleic acid found in cells. It contains genetic instructions that cells need to make proteins. Ribosomes are structures in the cytoplasm where proteins are made. They consist of RNA and proteins. These four components are found in all cells. They are found in the cells of organisms as different as bacteria and people. How did all known organisms come to have such similar cells? The answer is evolution. The similarities show that all life on Earth evolved from a common ancestor. Besides the four parts listed above, many cells also have a nucleus. The nucleus of a cell is a structure enclosed by a membrane that contains most of the cells DNA. Cells are classified in two major groups based on whether or not they have a nucleus. The two groups are prokaryotic cells and eukaryotic cells. Prokaryotic cells are cells that lack a nucleus. The DNA in prokaryotic cells is in the cytoplasm, rather than enclosed within a nuclear membrane. All the organisms in the Bacteria and Archaea Domains have prokaryotic cells. No other organisms have this type of cell. Organisms with prokaryotic cells are called prokaryotes. They are all single-celled organisms. They were the first type of organisms to evolve. They are still the most numerous organisms today. You can see a model of a prokaryotic cell in Figure 3.3. The cell in the figure is a bacterium. Notice how it contains a cell membrane, cytoplasm, ribosomes, and several other structures. However, the cell lacks a nucleus. The cells DNA is circular. 
 Question: The smallest unit of living things that can carry out the chemical reactions of life is the
[EX A]: cell

[EX Q]: Context: Assume that a school bus, like the one in Figure 12.2, passes by as you stand on the sidewalk. Its obvious to you that the bus is moving. It is moving relative to you and the trees across the street. But what about to the children inside the bus? They arent moving relative to each other. If they look only at the other children sitting near them, they will not appear to be moving. They may only be able to tell that the bus is moving by looking out the window and seeing you and the trees whizzing by. This example shows that how we perceive motion depends on our frame of reference. Frame of reference refers to something that is not moving with respect to an observer that can be used to detect motion. For the children on the bus, if they use other children riding the bus as their frame of reference, they do not appear to be moving. But if they use objects outside the bus as their frame of reference, they can tell they are moving. What is your frame of reference if you are standing on the sidewalk and see the bus go by? How can you tell the bus is moving? The video at the URL below illustrates other examples of how frame of reference is related to motion. MEDIA Click image to the left or use the URL below. URL: Did you ever go to a track meet like the one pictured in Figure 12.3? Running events in track include 100-meter sprints and 2000-meter races. Races are named for their distance. Distance is the length of the route between two points. The length of the route in a race is the distance between the starting and finishing lines. In a 100-meter sprint, for example, the distance is 100 meters. The SI unit for distance is the meter (1 m = 3.28 ft). Short distances may be measured in centimeters (1 cm = 0.01 m). Long distances may be measured in kilometers (1 km = 1000 m). For example, you might measure the distance a frogs tongue moves in centimeters and the distance a cheetah moves in kilometers. Maps can often be used to measure distance. Look at the map in Figure 12.4. Find Mias house and the school. You can use the map key to directly measure the distance between these two points. The distance is 2 kilometers. Measure it yourself to see if you agree. Things dont always move in straight lines like the route from Mias house to the school. Sometimes they change direction as they move. For example, the route from Mias house to the post office changes from west to north at the school (see Figure 12.4). To find the total distance of a route that changes direction, you must add up the distances traveled in each direction. From Mias house to the school, for example, the distance is 2 kilometers. From the school to the post office, the distance is 1 kilometer. Therefore, the total distance from Mias house to the post office is 3 kilometers. You Try It! Problem: What is the distance from the post office to the park in Figure 12.4? Direction is just as important as distance in describing motion. For example, if Mia told a friend how to reach the post office from her house, she couldnt just say, "go 3 kilometers." The friend might end up at the park instead of the post office. Mia would have to be more specific. She could say, "go west for 2 kilometers and then go north for 1 kilometer." When both distance and direction are considered, motion is a vector. A vector is a quantity that includes both size and direction. A vector is represented by an arrow. The length of the arrow represents distance. The way the arrow points shows direction. The red arrows in Figure 12.4 are vectors for Mias route to the school and post office. If you want to learn more about vectors, watch the videos at these URLs: (5:27) MEDIA Click image to the left or use the URL below. URL: You Try It! Problem: Draw vectors to 
 Question: When both distance and direction are considered, motion
[EX A]: is a vector.

[EX Q]: Context: Playing again without Calvin Johnson, the Lions fell behind the visiting New Orleans Saints by two scores on two separate occasions, before mounting a dramatic comeback in the final minutes of the game. New Orleans had three of the first four scoring plays of the game. Drew Brees hit Austin Johnson with a 14-yard TD pass, Shayne Graham made good on a 27-yard field goal, and Kenny Stills caught a 46-yard TD pass from Brees. Meanwhile, the Lions could only muster a 21-yard field goal by Matt Prater, falling behind 17-3. Detroit closed the gap to 17-10 in the third quarter after a 1-yard TD run by Joique Bell. Two more Shayne Graham field goals, however, gave the Saints a seemingly comfortable 23-10 lead with 5:24 to play in the game. With under four minutes to play, Matthew Stafford connected with Golden Tate on a 73-yard catch-and-run, making the score 23-17. On the Saints' next possession, Glover Quin picked off a third-and-ten Drew Brees pass, returning it to the New Orleans 14-yard line. At the 1:48 mark, Corey Fuller made a leaping catch of a 5-yard TD pass from Stafford for the winning touchdown in a 24-23 game. The Lions' defense held off the Saints in four downs, then the offense ran out the clock for the win. 
 Question: Which team score the fewest points?
[EX A]:
saints