题目

The teacher found ____ difficult to decide ____ he would take with him to attend the conference.     A. it; whom          B. himself; who       C. this; whom        D. that; who   答案：A第一空用形式宾语it,第二空可以用who或whom引导宾语从句并在从句中作take的宾语。人体细胞中有________对染色体．决定性别的染色体叫做性染色体，女性的性别染色体组成是________，男性的性别染色体组成是________．