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: Last week a study of one hundred ninety-nine countries confirmed what many people may have already noticed. People around the world are getting fatter. The study found that obesity has almost doubled since 1980. Majid Ezzati, who led the research team, says the results show that obesity, high blood pressure and high blood pressure are no longer just found in wealthy nations. These are now worldwide problems. The study appeared shows that in 2008, almost ten percent of men were obese. That was up from about five percent in 1980. That same year, almost eight percent of women were obese. By 2008, the rate of obesity among women was almost fourteen percent. Obesity is commonly measured by body mass index , or BMI. This is a measure of a person's weight in relation to height. A person with a BMI of twenty-five to twenty-nine is considered overweight. The World Health Organization defines obesity as a body mass index of thirty or more. Pacific island nations have an average BMI of around thirty-five -- the highest in the world. But the study found that the United States had the single highest average among wealthy countries. Men and women had an average BMI of over twenty-eight. New Zealand was next. Japan had the lowest, at about twenty-two for women and twenty-four for men. The report had some good news, however, about high blood pressure. The percentage of people with this major cause of heart attacks and strokes has fallen since 1980. Dr. Ezzati credits improved testing and treatment in wealthy countries. He says a decrease in the use of salt and unhealthful fats probably also helped. In the United States, new guidelines urge Americans to reduce salt, sugar and fatty meats and to eat more fish and whole grains. People are being urged to choose water over sugared drinks and to eat more fruits and vegetables. But whatever they eat, Americans are being urged to follow new advice from the government: eat less. 
 Answer: thirty
A:
According to the World Health Organization, a person is considered obese if he / she has a BMI of over  _  .