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: The south and east of the Great Lakes is famous for the huge amounts of snow it receives. When the snow starts to fall every year, people start discussing the phrase "lake-effect snow". Lake-effect snow which is influenced by the movement of cold air over the relatively warm water of the Great Lakes often comes in late autumn and early winter. Because of the at least 20 degrees' difference between the lake water and the overrunning air, it's easy to form huge amounts of snow. As the cool air crosses the water of Great Lakes, the lowest levels of the atmosphere begin to warm and pick up moisture. This newly warmed atmosphere is lighter than the cold air above it, so it starts rising. As the changed air continues to climb higher and higher, it finally meets much colder atmosphere which changes the moisture into water drops and ice, forming clouds. After this course repeats a number of times, the clouds become heavier and heavier, and then they are changed into snow and fall down. The most important point that decides the amount of snowfall is the direction of the wind. If the wind runs perpendicularly across the lake, there won't be plenty of time for clouds to develop. However, if the wind runs in the opposite direction, clouds will form easily. The longer the cold air travels over the lake, the more moisture it is able to produce, which leads to a greater amount of snow. The largest amount of the lake-effect snow was found across the U.P. of Michigan, the northwestern Pennsylvania and the far southwestern and northwestern New York, which are all along the south or east of the Great Lakes. It has been over 100 inches of snowfall in a winter season. 
 Answer: the direction of the wind

A: The level of the snowfall depends on   _  .
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Q: Article: A green house is a building made of glass which is used for keeping warm when the outside temperature is low. In a similar way there are several gases in the atmosphere (mixture of gases that surround the earth) which trap the heat produced by the sun and prevent it from escaping. These gases are known as "greenhouse gases". And the way in which they trap heat in the atmosphere is called the "greenhouse effect". This is not simply air pollution. Most of the main greenhouse gases exist naturally in small amounts in our atmosphere, and without them the earth would be 30 degrees colder and human life would not exist. In other words, the greenhouse effect is a natural course which is to some degree helpful to us. The problem is that in the last century and a half, we have been putting too many of these gases into the earth's atmosphere by burning large quantities of coal and oil and by cutting down forest. The rapid increase in greenhouse gases is making the world warmer. The world's temperature has already gone up by half a degree this century, and the sea level has risen by 10 centimetres. If the amount of carbon dioxide in the atmosphere doubles, there will probably be a rise in the earth's temperature of between I and 4degC;. This may seem a small increase, but it would be enough to cause major changes in geography and agriculture. Large areas of the world would be flooded, and some areas would become dry and unable to produce crops. It is important, too, to consider that there may be a delay of about 30 years in the greenhouse effect. This means that we are probably experiencing only now the effect of the gases put into the atmosphere before the 1960s. Since then, our use of these gases has greatly increased. 
 Answer: a natural course that is to a certain degree useful to us

A: According to the passage, we can know "greenhouse effect" means  _  .
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Q: Article: Since the first Earth Day in 1970, Americans have gotten a lot "greener" toward the environment. "We didn't know at that time that there even was an environment, let alone that there was a problem with it," says Bruce Anderson, president of Earth Day USA. But what began as nothing important in public affairs has grown into a social movement. Business people, political leaders, university professors, and especially millions of grass-roots Americans are taking part in the movement. "The understanding has increased many, many times," says Gaylord Nelson, the former governor from Wisconsin, who thought up the first Earth Day. According to US government reports, emissions  from cars and trucks have dropped from 10.3 million tons a year to 5.5 tons. The number of cities producing CO beyond the standard has been reduced from 40 to 9. Although serious problems still remain and need to be dealt with, the world is a safer and healthier place. A kind of "Green thinking " has become part of practices. Great improvement has been achieved. In 1988 there were only 600 recycling programs, today in 1995 there are about 6,600. Advanced lights, motors, and building designs have helped save a lot of energy and therefore prevented pollution. Twenty-five years ago, there were hardly any education programs for environment. Today, it's hard to find a public school, university, or law school that does not have such a kind of program. "Until we do that, nothing else will change!" says Bruce Anderson. 
 Answer: environmental problems

A:
According to Anderson, before 1970, Americans had little idea about   _  .
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