某生物的测交后代中只有两种表现型(1∶1),则此生物 () A.一定含有一对等位基因 B.一定产生两种比值相等的配子 C.一定不含有等位基因 D.不可能含有两对以上的等位基因 答案:B重新排列下面句子的顺序,使它成为一段通顺的对话,并将其标号填入题前括号内。( ) Oh, really? ( ) Sure. Here you are. ( ) I have a toy dog. ( ) Thank you. ( ) Oh, it's nice! ( ) Thanks. ( ) I like it. ( ) May I have a look?