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.

Example Input: Context: Humans did not reach space until the second half of the 20th century. They needed somehow to break past Earths gravity. A rocket moves rapidly in one direction. The device is propelled by particles flying out of it at high speed in the other direction. There are records of the Chinese using rockets in war against the Mongols as early as the 13th century. The Mongols then used rockets to attack Eastern Europe. Early rockets were also used to launch fireworks. Rockets were used for centuries before anyone could explain how they worked. The theory came about in 1687. Isaac Newton (16431727) described three basic laws of motion, now referred to as Newtons Laws of Motion: 1. An object in motion will remain in motion unless acted upon by a force. 2. Force equals mass multiplied by acceleration. 3. To every action, there is an equal and opposite reaction. Which of these three best explains how a rocket works? Newtons third law of motion. When a rockets propulsion pushes in one direction, the rocket moves in the opposite direction, as seen in the Figure 23.12. For a long time, many people believed that a rocket wouldnt work in space. There would be nothing for the rocket to push against. But they do work! Fuel is ignited in a chamber. The gases in the chamber explode. The explosion creates pressure that forces the gases out of one side of the rocket. The rocket moves in the opposite direction, as shown in Figure 23.13. The force pushing the rocket is called thrust. For centuries, rockets were powered by gunpowder or other solid fuels. These rockets could travel only short distances. Around the turn of the 20th century, several breakthroughs took place. These breakthroughs led to rockets that could travel beyond Earth. Liquid fuel gave rockets enough power to escape Earths gravity (Figure 23.14). By using multiple stages, empty fuel containers could drop away. This reduced the mass of the rocket so that it could fly higher. Rockets were used during World War II. The V2 was the first human-made object to travel high enough to be considered in space (Figure 23.15). Its altitude was 176 km (109 miles) above Earths surface. Wernher von Braun was a German rocket scientist. After he fled Germany in WWII, he helped the United States develop missile weapons. After the war, von Braun worked for NASA. He designed the Saturn V rocket (Figure One of the first uses of rockets in space was to launch satellites. A satellite is an object that orbits a larger object. An orbit is a circular or elliptical path around an object. Natural objects in orbit are called natural satellites. The Moon is a natural satellite. Human-made objects in orbit are called artificial satellites. There are more and more artificial satellites orbiting Earth all the time. They all get into space using some sort of rocket. Why do satellites stay in orbit? Why dont they crash into Earth due to the planets gravity? Newtons law of universal gravitation describes what happens. Every object in the universe is attracted to every other object. Gravity makes an apple fall to the ground. Gravity also keeps you from floating away into the sky. Gravity holds the Moon in orbit around Earth. It keeps Earth in orbit around the Sun. Newton used an example to explain how gravity makes orbiting possible. Imagine a cannonball launched from a high mountain, as shown in Figure 23.17. If the cannonball is launched at a slow speed, it will fall back to Earth. This is shown as paths (A) and (B). Something different happens if the cannonball is launched at a fast speed. The Earth below curves away at the same rate that the cannonball falls. The cannonball then goes into a circular orbit, as in path (C). If the cannonball is launched even faster, it could go into an elliptical orbit (D). It might even leave Earths gravity and go into space (E). Unfortunately, Newtons idea would not work in real life. A cannonball launched at a fast speed from Mt. Everest would not go into orbit. 
 Question: The first rocket to travel into space was used during
Example Output: world war ii.

Example Input: Context: Between 1911 and 1912, over 1,000 Somalis from Mogadishu, the then capital of Italian Somaliland, served as combat units along with Eritrean and Italian soldiers in the Italo-Turkish War. Most of the troops stationed never returned home until they were transferred back to Italian Somaliland in preparation for the invasion of Ethiopia in 1935. The first disembarkation of Italian troops occurred on October 10. The Italian contingent of 20,000 troops was deemed sufficient to accomplish the conquest at the time. Tobruk, Derna and Khoms were easily conquered, but the same was not true for Benghazi. The first true setback for the Italian troops happened on October 23, when poor placement of the troops near Tripoli led them to be almost completely encircled by more mobile Arab cavalry, backed by some Turkish regular units. The attack was portrayed as a simple revolt by the Italian press, but it nearly annihilated much of the small Italian expeditionary corps. The corps was consequently enlarged to 100,000 men who had to face 20,000 Arabs and 8,000 Turks. The war turned into one of position. Even some of the earliest examples of utilisation in modern warfare of armoured cars and air power by the Italian forces had little effect on the initial outcome. However, the war was notable for the first military use of heavier-than-air craft. Capitano Carlo Piazza flew the first military reconnaissance flight on 23 October 1911. A week later, Sottotenente Giulio Gavotti dropped four grenades on Taguira and Ain Zara in history's first aerial bombing. 
 Question: Aerial bombing by who?
Example Output: giulio gavotti

Example Input: Context: The cell membrane is like the bag holding the Jell-O. It encloses the cytoplasm of the cell. It forms a barrier between the cytoplasm and the environment outside the cell. The function of the cell membrane is to protect and support the cell. It also controls what enters or leaves the cell. It allows only certain substances to pass through. It keeps other substances inside or outside the cell. The structure of the cell membrane explains how it can control what enters and leaves the cell. The membrane is composed mainly of two layers of phospholipids. Figure 3.8 shows how the phospholipids are arranged in the cell membrane. Each phospholipid molecule has a head and two tails. The heads are water loving (hydrophilic), and the tails are water fearing (hydrophobic). The water-loving heads are on the outer surfaces of the cell membrane. They point toward the watery cytoplasm within the cell or the watery fluid that surrounds the cell. The water-fearing tails are in the middle of the cell membrane. Hydrophobic molecules like to be near other hydrophobic molecules. They fear being near hydrophilic molecules. The opposite is true of hydrophilic molecules. They like to be near other hydrophilic molecules. They fear being near hydrophobic molecules. These likes and fears explain why some molecules can pass through the cell membrane while others cannot. Hydrophobic molecules can pass through the cell membrane. Thats because they like the hydrophobic interior of the membrane and fear the hydrophilic exterior of the membrane. Hydrophilic molecules cant pass through the cell membrane. Thats because they like the hydrophilic exterior of the membrane and fear the hydrophobic interior of the membrane. You can see how this works in the video at this link: . MEDIA Click image to the left or use the URL below. URL: Cytoplasm is everything inside the cell membrane (except the nucleus if there is one). It includes the watery, gel-like cytosol. It also includes other structures. The water in the cytoplasm makes up about two-thirds of the cells weight. It gives the cell many of its properties. Why does a cell have cytoplasm? Cytoplasm has several important functions. These include: suspending cell organelles. pushing against the cell membrane to help the cell keep its shape. providing a site for many of the biochemical reactions of the cell. Crisscrossing the cytoplasm is a structure called the cytoskeleton. It consists of thread-like filaments and tubules. The cytoskeleton is like a cellular skeleton. It helps the cell keep its shape. It also holds cell organelles in place within the cytoplasm. Figure 3.9 shows several cells. In the figure, the filaments of their cytoskeletons are colored green. The tubules are colored red. The blue dots are the cell nuclei. Eukaryotic cells contain a nucleus and several other types of organelles. These structures carry out many vital cell functions. The nucleus is the largest organelle in a eukaryotic cell. It contains most of the cells DNA. DNA, in turn, contains the genetic code. This code tells the cell which proteins to make and when to make them. You can see a diagram of a cell nucleus in Figure 3.10. Besides DNA, the nucleus contains a structure called a nucleolus. Its function is to form ribosomes. The membrane enclosing the nucleus is called the nuclear envelope. The envelope has tiny holes, or pores, in it. The pores allow substances to move into and out of the nucleus. The mitochondrion (mitochondria, plural) is an organelle that makes energy available to the cell. Its like the power plant of a cell. It uses energy in glucose to make smaller molecules called ATP (adenosine triphosphate). ATP packages energy in smaller amounts that cells can use. Think about buying a bottle of water from a vending machine. The machine takes only quarters, and you have only dollar bills. The dollar bills wont work in the vending machine. Glucose is like a dollar bill. It contains too much energy for cells to use. ATP is like a quarter. It contains just the right amount of energy for use by cells. A ribosome is a small 
 Question: A cell membrane consists mainly of
Example Output:
phospholipids.