In this task, you're given an article and an answer. Your task is to generate the fill-in-the-blank question for this answer based on the given article. The blanks are always at the end of the question, and can be filled with more than one word or phrase.

Q: Article: Overlooking the swollen banks of the Missouri River at Omaha's riverfront landing, one scientist has an important explanation for the past three months of flooding .While many consider the flood to be man-made, a result of water released by the US. Army Corps of Engineers upriver, his theory aims to look deeper into the root of the problem. "The Missouri River is flooding," said Dr. James Hansen, Director of NASA's Goddard Institute for Space Studies, during a visit to Omaha on Tuesday."We've had floods that usually only happen once in every hundred years a couple of times on the Missouri River recently. That's one of the expected consequences of the increasing level of atmospheric carbon dioxide." Hansen, who is considered to be one of the world's leading experts on global warming , said the Missouri River is an example of how global warming is affecting the earth ."Unless you do statistics ,and you see that the frequency of these events is changing , it's not so easy to see that changes are occurring , because the climate system has large inertia ,"he said . Hansen explained, "The ocean is four kilometers deep, and the ice sheets are two or three kilometers thick , so they don't respond immediately as we begin to change the atmospheric composition .We've only experienced about half of the warming that will be caused by the gases already in the atmosphere .The full effect is going to be felt by our children and grandchildren .And if we continue to increase the amount of CO2, the effect will be even larger." Hansen drew a comparison, "If we spend more money than what we're taking in , we're leaving a debt for our children and grandchildren to deal with ."According to Hansen, the responsibility lies in effective policy making to fight against global warming .That includes a gradual reduction in carbon emissions .Hansen suggests that a rising price be placed on carbon emissions, which should be collected from the fossil fuel companies at the first sale . Without effective measures taken by the government, Hansen said the public could expect more of the recent extreme weather patterns,, including more severe droughts and floods in the decades ahead .
Answer: the army releasing water upriver

A: Many people think the reason for the flooding of the Missouri River is _ .
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Q: Article: Cats are creatures of habit. They like to go to sleep about the same time every day and for a certain length of time. They seem to have a natural clock inside them that tells them when to sleep. Cats increase their regular sleep with occasional cat naps . Some experts feel that humans could also benefit from this habit. Cat naps help to build up energy in the body. They are also a good way to get rid of trouble! Since cats have the same moods as humans, some experts believe that people can improve their moods. People might become happier. A number of famous people have copied cats by taking cat naps during the day. The naps would usually last from 15 to 30 minutes. Winston Churchill took cat naps. So did Presidents Harry Truman, John F. Kennedy, and Lyndon B. Johnson. These famous men were known for their energy. They were also able to work long hours, often into the night. Napping was their secret.
Answer: take naps when they are not happy

A: From this selection we know that cats _ .
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Q: Article: Are you looking for something to do? You might like to try one of these four experiences. Crocodile watching Do you fancy getting up close to some of the most terrifying animals on earth? Crocosaurus Cove, in Darwin (Australia) has the "Cage of Death". It's an enclosure that's lowered into a pool. This gives you a 360 degree view of a crocodile as it's being fed. The cable broke once and the cage sank to the bottom, but they've fixed it since then. Edge walk How about walking along the edge of a building several hundred meters up in the air? If that sounds like fun, head off to the CN Tower in Toronto (Ontario, Canada). Built in 1976, the tower is 553.33 meters tall. The Edge walk consists of a 20-30 minute stroll along a 1.5 meter wide platform that runs around the tower's restaurant roof. During the walk, you're encouraged to lean forwards as you look over Toronto's skyline . Plastic ball rolling Do you fancy rolling down a hill in a plastic ball? Plastic ball rolling is popular all over the world, but the place to give it a go is in Rotorua (New Zealand). Brother David and Andrew Akers came up with the idea in 1994. A typical orb is about 3 meters in diameter, with an inner orb size of about 2 meters. There's no brake or steering mechanism, but the inner layer of the plastic ball helps absorb the shock. Volcano bungee jumping If you're looking for the adventure of a lifetime, how about going bungee jumping off a helicopter into the crater of a live volcano? As part of the jumping, a helicopter ride takes you to the Villarreal volcano, one of the most active in Chile. Once you're at the drop zone, you leap off the helicopter and fall into the volcano. Finally, you enjoy the ride back to the airport flying at 130kph. Attracted by the above? If so, please contact us. Only half price from March 22 to April 25th. For more information, please click here.
Answer: watched crocodiles in the "Cage of Death" in Darwin

A:
According to the passage, there was an accident once when people _ .
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