题目

精子形成过程中，减数第一次分裂中期的染色体数和DNA之比（ ）A. 1:2 B. 2:1 C. 1:1 D. 4:1 答案：【答案】A【解析】由于减数第一次分裂中每一条染色体含有2条染色单体，所以减数第一次分裂后期的染色体数和DNA之比1：2，故选A。I _____ to take a holiday this summer, but I had to change my plan . 　 A. would hope 　 B. was hoping 　 C. had been hoped 　 D. had hoped