They were ahead during the first half of the match, but they ________ in the last five minutes. A.were beating B.beat C.were beaten D.had been beaten 答案:C 解析: 略关于在自然条件下,某机交配种群中等位基因A、a频率的叙述,错误的是 A.在某种条件下两种基因的频率可以相等 B.该种群基因频率的变化只与环境的选择作用有关 C.一般来说,频率高的基因所控制的性状更适应环境 D.持续选择条件下,一种基因的频率可以降为零