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.
One example is below.
Q: Article: Homework can put you in a badmood , and that might actually be a good thing. Researchers from the University of Plymouth in England doubted whether mood might affect the way kids learn. To find out the answer, they did two experiments with children. The first experiment tested 30 kids. Someshapes were hidden inside a different, larger picture. The kids had to find the small shapes while sitting in a room with either cheerful or sad music playing in the background. To test their mood, the scientists asked the kids to point to one of five faces, from happy to sad. Children who listened to cheerful music tended to point to the smiley faces while the others pointed to the unhappy ones. The researchers found that sad kids took at least a second less to find the small shapes. They also found an average of three or four more shapes. In the second experiment, 61 children watched one of two scenes from a film. One scene was happy, and the other was sad. Just like in the first experiment, kids who saw the sad scene acted better compared to the others. The researchers guessed that feeling down makes people more likely to focus on a problem or difficult situation. Not all scientists agree with them, however. Other studies argued that maybe, that cheerful music in the first experiment distracted kids from finding shapes. While scientists work on finding out the answers, it still might be wise to choose when to do your tasks according to your mood. After eating a delicious ice cream, for example, write an essay. 
 Answer: whether mood affects their learning ability
A: Researchers did experiments on kids in order to find out _ .
Rationale: It is clearly mentioned in the article that to the check effect of mood on children is the main purpose of the experiment.
Q: Article: It is believed that it took about 800 thousand to 1 million years for the earth's population to reach the 250 million total which existed at the end of the first century AD. For some time after that, disease, famine  and war kept the population increase down to a rate of 1 percent a year so that more than 15 centuries passed before the population reached 500 million. But in the next 250 years, up to 1850, the population of the world shot to 1 billion and today it has reached 3.5 billion. Scientists say that in the next 35 years the population of the world will double, reaching almost 7 billion by the year 2010. When experts are asked what are the most effective measures that can stop over population, they reply that at least three measures can be considered. (A) Increasing sources and supply of food for under-developed countries. (B) Increasing the industrialization of under- developed countries. (C) Controlling birth. The experts add, however, that none of the above measures can be effective by itself, and that all must be combined into one whole program. They also agree that without controlling of births, any other measures are doomed   to failure. 
 Answer: still increased very fast
A:
The population   _   because of disease, famine and war.