题目

某DNA分子含嘌呤碱基4000个，胸腺嘧啶与腺嘌呤之和占60%；其中一条链的胞嘧啶占12%，则该链互补链的胞嘧啶数是（ ）A.660个 B.800个C.1120个 D.2240个 答案：【答案】C【解析】试题据题意，嘌呤数=嘧啶数=4000，因此DNA碱基数=8000，A+T=60%,推出A=T=30%推出G=C=20%，其中一条链的胞嘧啶占该链12%，占DNA双链6%，另一条链胞嘧啶占该DNA双链为20%-6%=14%，个数为14%×8000=1120个，故C正确。The exchange student from Australia is a friend of mine. She enjoyed ________ at the Art Festival held in Beijing yesterday.A.herB.himC.herselfD.himself