In this task, you're given an article, a question which often contains a blank and four options (associated with "A", "B", "C", "D"). Your task is to find the correct answer (from the given options) for the question from the given article and return one of the options from "A", "B", "C", and "D". Do not generate anything else apart from one of the following characters: "A", "B", "C", "D". There is only one correct answer for each question.
Example: Article: Homework can put you in a bad mood , 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.
Question: Researchers did experiments on kids in order to find out _ .
Options: (A) how they really feel when they are learning (B) whether mood affects their learning ability (C) what methods are easy for kids to learn (D) the relationship between sadness and happiness
Example solution: B
Example explanation: It is clearly mentioned in the article that to the check effect of mood on children is the main purpose of the experiment. So, B is the correct answer.

Problem: Article: Do you want to live another 100 years or more? Some experts say that scientific progress will one day help humans to last tens of years longer than what is now seen as the natural limit of the human life span . " I think _ ," said Michael Zey, a Montclair State University business professor and author of two books on the future. " I think by 2075 we will see it and that's a conservative estimate ." At the conference in San Francisco, Donald Louria, a professor at New Jersey Medical School in Newark said progress in using genes as well as nanotechnology makes it likely that humans will live in the future beyond what has been possible in the past. " There is a great push so that people can live from 120 to 180 years," he said. " Some have suggested that there is no limit and that people could live to 200 or 300 or 500 years." However, many scientists who research into aging are doubtful about _ and say the human body is just not designed to last about 120 years. Even with healthier lifestyles and less disease, they say failure of the brain and organs will finally lead all humans to death. Scientists also disagree on what kind of life the super aged might live. "It remains to be seen whether you could be healthy enough to have good quality of life when you pass 120." said Leonard Poon, director of the University of Georgia Gerontology Center. " At present people who could get to that point are not in good health at all."
Question: By saying " we are knocking at the door immortality", Michael Zey means _ .
Options: (A) they believe that there is no limit of living (B) they are sure to find the truth about long living (C) they have got some ideas about long living (D) they are able to make people live beyond the present life span
Solution: C