题目

基因A和a的关系是（ ） A．位于同一条染色体上 B．位于一对染色体的相同位上 C．位于不同的染色体上 D．位于一对染色体的不同位置上 答案：B －I'm sorry, but I don't quite follow you．Did you say you wanted to return on September 20? －Sorry, I ________ myself clear．We want to return on October 20． [　　] A． hadn't made B． wouldn't make C． don't make D． haven't made