题目

Ten years ago the population of our village was that of theirs. A . as twice large as B . twice as large as C . twice as much as D . as twice much as 答案：BHIV、流感病毒属于RNA病毒，具有逆转录酶，如果它决定某性状的一段RNA含碱基A＝19%、C＝26%、G＝32%，则通过逆转录过程形成的双链DNA中含有的碱基A占碱基总数的 (　　)A．19% B．21% C．23%D．42%