问题
单项选择题 A1/A2型题
控制病毒遗传变异的主要成分是（）。
A.染色体
B.衣壳
C.壳粒
D.核酸
E.包膜
答案
参考答案：D
解析：核酸是病毒的遗传物质，是病毒遗传和感染的物质基础。
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控制病毒遗传变异的主要成分是（）。
A.染色体
B.衣壳
C.壳粒
D.核酸
E.包膜
参考答案：D
解析：核酸是病毒的遗传物质，是病毒遗传和感染的物质基础。
Years ago, in a small fishing village in Holland, a young boy taught the world about  the rewards of unselfish service.Because the entire village lived on fishing, a volunteer rescue team was needed in case of emergency. One night, the winds 36 , the clouds burst and a strong storm overturned a fishing boat at sea. The crew in trouble 37 the SOS. The captain of the rescue rowboat team 38 the alarm and the villagers 39 in the town square overlooking the sea. When the team started their rowboat fought their way through the wild waves, the villagers waited 40 on the beach, holding lamps to 41 the way back. An hour later, the rescue boat reappeared through the fog and the 42 villagers ran to greet them. Falling 43 on the sand, the volunteers reported that the rescue boat could not hold any more 44 and they had to leave one man behind. Even one more passenger would have surely 45 the rescue boat and all would have been lost. 46 , the captain called for another volunteer team to 47 the survivor. Sixteen-year-old Hans stepped forward. His mother grabbed his arm, crying, "please don't go. Your father 48 in a shipwreck (船只失事) 10 years ago and your elder brother, Paul, has been lost 49 for three weeks. Hans, you are all I have left." Hans replied, "Mother, I have to go. 50 everyone said I can't go, let someone else do it? Mother, this time I have to do my duty. When the call for service 51 , we all need to take our turn and do our part. Hans kissed his mother, joined the team and 52 into the night. " Another hour passed, which seemed to Hans' mother like a century. 53 the rescue boat dashed through the fog with Hans standing up in the bow. 54 his hands, the captain called, "did you find the lost man?" 55 able to control himself, Hans excitedly cried back, "Y  es, we found him. Tell  my mother it's my elder brother, Paul!"
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