题目

听下面一段较长对话，回答以下小题。【1】What does the man probably think of his time?A. Boring. B. Tiring. C. Fun.【2】When did the old woman begin to paint?A. In her early 60s. B. In her early 70s. C. In her middle 70s.【3】Why doesn't the man learn to paint?A. He has no interest in it.B. No one wants to teach him.C. He doesn't think he's good at it.【4】What does the man decide to do in the end?A. Learn to sing.B. Learn to play ping-pong.C. Visit the other retired people.某生物碱基的组成是嘌呤碱基占58%，嘧啶碱基占42%，此生物不可能是（  ） A.烟草    B.小麦   C.烟草花叶病毒    D.噬菌体