F: How do you know how old a star is? ,M: For most stars, we find its age from how big it is. We can know its size from the amount of light it puts out and its color. Then the size tells us how long a star will live. Big stars live a short life, while small stars live much longer. ,F: I've always wondered if there is an end in space. Do you think scientists have found the answer? ,M: This is a difficult question. The truth is that we have no idea. We currently don't have a way of testing it. But some scientists will come up with a way in the future. I have faith in it.
(A) F: You are right. Since the scientists have already found the answer, there is an end in space. (B) F: You are telling the truth. There are still unsolved problems in the universe nowadays. (C) F: That is right. Although there are unsolved problems, scientists can solve them tonight. (D) F: I am sorry. You spoke so rapidly that I did not catch the meaning of what you said. Could you repeat that?
B