Given a context passage, generate a question from the passage such that its answer is shortest continous span from the passage.

Input: Consider Input: Like water and carbon, nitrogen is also repeatedly recycled through the biosphere. This process is called the nitrogen cycle. Nitrogen is one of the most common elements in living organisms. It is important for creating both proteins and nucleic acids, like DNA. The air that we breathe is mostly nitrogen gas (N2 ), but, unfortunately, animals and plants cannot use the nitrogen when it is a gas. In fact, plants often die from a lack of nitrogen even through they are surrounded by plenty of nitrogen gas. Nitrogen gas (N2 ) has two nitrogen atoms connected by a very strong triple bond. Most plants and animals cannot use the nitrogen in nitrogen gas because they cannot break that triple bond. In order for plants to make use of nitrogen, it must be transformed into molecules they can use. This can be accomplished several different ways ( Figure 1.1). Lightning: When lightening strikes, nitrogen gas is transformed into nitrate (NO3 ) that plants can use. Nitrogen fixation: Special nitrogen-fixing bacteria can also transform nitrogen gas into useful forms. These bacteria live in the roots of plants in the pea family. They turn the nitrogen gas into ammonium (NH4 + ) (a process called ammonification). In water environments, bacteria in the water can also fix nitrogen gas into ammonium. Ammonium can be used by aquatic plants as a source of nitrogen. Nitrogen also is released to the environment by decaying organisms or decaying wastes. These wastes release nitrogen in the form of ammonium. Ammonium in the soil can be turned into nitrate by a two-step process completed by two different types of bacteria. In the form of nitrate, nitrogen can be used by plants through the process of assimilation. It is then passed along to animals when they eat the plants. Turning nitrate back into nitrogen gas, the process of denitrification, happens through the work of denitrifying bacteria. These bacteria often live in swamps and lakes. They take in the nitrate and release it back to the atmosphere as nitrogen gas. Just like the carbon cycle, human activities impact the nitrogen cycle. These human activities include the burning of fossil fuels, which release nitrogen oxide gasses into the atmosphere. Releasing nitrogen oxide back into the atmosphere leads to problems like acid rain.

Output: the initial step of producing a nitrogen containing compound from nitrogen in the soil is


Input: Consider Input: People have been using sound to make music for thousands of years. They have invented many different kinds of musical instruments for this purpose. Despite their diversity, however, musical instruments share certain similarities. All musical instruments create sound by causing matter to vibrate. The vibrations start sound waves moving through the air. Most musical instruments use resonance to amplify the sound waves and make the sounds louder. Resonance occurs when an object vibrates in response to sound waves of a certain frequency. In a musical instrument such as a guitar, the whole instrument and the air inside it may vibrate when a single string is plucked. This causes constructive interference with the sound waves, which increases their amplitude. Most musical instruments have a way of changing the frequency of the sound waves they produce. This changes the pitch of the sounds. There are three basic categories of musical instruments: percussion, wind, and stringed instruments. In Figure Researchers at Lawrence Berkeley National Laboratory are pioneering a new way to recover 100-year-old record- ings. Found on fragile wax cylinders and early lacquer records, the sounds reveal a rich acoustic heritage, including languages long lost. For more information on how to recover recordings, see [Link] MEDIA Click image to the left or use the URL below. URL: Ultrasound has frequencies higher than the human ear can detect (higher than 20,000 hertz). Although we cant hear ultrasound, it is very useful. Uses include echolocation, sonar, and ultrasonography. Animals such as bats, whales, and dolphins send out ultrasound waves and use their echoes, or reflected waves, to identify the locations of objects they cannot see. This is called echolocation. Animals use echolocation to find prey and avoid running into objects in the dark. Figure 20.13 and the animation at the URL below show how a bat uses echolocation to locate insect prey. Sonar uses ultrasound in a way that is similar to echolocation. Sonar stands for sound navigation and ranging. It is used to locate underwater objects such as sunken ships or to determine how deep the water is. A sonar device is usually located on a boat at the surface of the water. The device is both a sender and a receiver (see Figure 20.14). It sends out ultrasound waves and detects reflected waves that bounce off underwater objects or the bottom of the water. If you watch the video at the URL below, you can see how sonar is used on a submarine. The distance to underwater objects or the bottom of the water can be calculated from the known speed of sound in water and the time it takes for the waves to travel to the object. The equation for the calculation is: Distance = Speed Time Assume, for example, that a sonar device on a ship sends an ultrasound wave to the bottom of the ocean. The speed of the sound through ocean water is 1437 m/s, and the wave travels to the bottom and back in 2 seconds. What is the distance from the surface to the bottom of the water? The sound wave travels to the bottom and back in 2 seconds, so it travels from the surface to the bottom in 1 second. Therefore, the distance from the surface to the bottom is: Distance = 1437 m/s 1 s = 1437 m You Try It! Problem: The sonar device on a ship sends an ultrasound wave to the bottom of the water at speed of 1437 m/s. The wave is reflected back to the device in 4 seconds. How deep is the water? Ultrasound can be used to "see" inside the human body. This use of ultrasound is called ultrasonography. Harmless ultrasound waves are sent inside the body, and the reflected waves are used to create an image on a screen. This technology is used to examine internal organs and unborn babies without risk to the patient. You can see an ultrasound image in Figure 20.15. You can see an animation showing how ultrasonography works at this URL: In this QUEST web extra, Stanford University astrophysicist Todd Hoeksema explains how solar sound waves are a vital ingredient to the science of helioseismology, in which the interior properties of the sun

Output: use of ultrasound to locate underwater objects


Input: Consider Input: On a brief trip back to London, earnest, bookish bacteriologist Walter Fane (Edward Norton) is dazzled by Kitty Garstin (Naomi Watts), a vivacious and vain London socialite. He proposes; she accepts ("only to get as far away from [her] mother as possible"), and the couple honeymoon in Venice. They travel on to Walter's medical post in Shanghai, where he is stationed in a government lab studying infectious diseases. They find themselves ill-suited, with Kitty much more interested in parties and the social life of the British expatriates. Kitty meets Charles Townsend (Liev Schreiber), a married British vice consul, and the two engage in a clandestine affair. When Walter discovers his wife's infidelity, he seeks to punish her by threatening to divorce her on the grounds of adultery, if she doesn't accompany him to a small village in a remote area of China. He has volunteered to treat victims of an unchecked cholera epidemic sweeping through the area. Kitty begs to be allowed to divorce him quietly, but he refuses, stating "Why should I put myself through the smallest trouble for you?" She hopes Townsend will leave his wife Dorothy and marry her. When she proposes this possibility to Charles, he declines to accept, despite earlier claiming to love Kitty. She is compelled to travel to the mountainous inland region with her husband. They embark upon an arduous, two-week-long overland journey, which would be considerably faster and much easier if they traveled by river, but Walter is determined to make Kitty as unhappy and uncomfortable as possible. Upon their arrival in Mei-tan-fu, she is distressed to discover they will be living in near squalor, far removed from everyone except their cheerful neighbor Waddington, a British deputy commissioner living with a young Chinese woman in relative opulence. Walter and Kitty barely speak to each other and, except for a cook and a Chinese soldier assigned to guard her, she is alone for long hours. After visiting an orphanage run by a group of French nuns, Kitty volunteers her services, and she is assigned to work in the music room. She is surprised to learn from the Mother Superior that her husband loves children, especially babies. In this setting, she begins to see him in a new light as she learns what a selfless and caring person he can be. When he sees her with the children, he in turn realizes she is not the shallow, selfish person he thought her to be. As Walter's anger and Kitty's unhappiness subside, their marriage begins to blossom in the midst of the epidemic crisis. She soon learns she is pregnant, but is unsure who the father is. Walter in love with Kitty again assures her it doesn't matter. The cholera epidemic takes many victims. As Walter and the locals are starting to get it under control, completely due to his importation of clean water through a system of aqueducts (as the local people did not understand water-borne infectious disease[2][bettersourceneeded]) cholera carrying refugees from elsewhere pour into the area, forcing Walter to set up a camp outside town. He contracts the disease and Kitty lovingly nurses him, but he dies, and she is devastated. Bereft and pregnant, she leaves China. Five years later, Kitty appears well-dressed and happy in London shopping with her young son Walter. They meet Townsend by chance on the street, and he suggests that Kitty meet with him. Asking young Walter his age, he realizes from the reply that he might have been the boy's father. Kitty rejects his overtures and walks away. When her son asks who Townsend is, she replies "No one important, darling".


Output: Where does Walter force Kitty to go with him?