题目

The firm was badly in      need of a manager who has      good knowledge of French.        A. a;/                                  B. the;a                              C. /;a                           D. /;the 答案：C一个基因中一个含氮碱基被替代可出现A.无意义突变B.移码突变C.错义突变D.不活动突变E.上述突变都可以出现