题目

Jessie felt her life so boring one summer day. She was tired of watching TV, she read all her books, and her friends were on vacation. She wanted something different to do. Suddenly, she saw the lawn mower(割草机) sitting in the yard.“Mom,” she shouted, “I think I will mow the lawn.” Her mom ran into the yard and said, “Oh no, you don’t. You’re too young to mow the law.”“I’m fourteen years old and know how to do it,” Jessie said. “Besides, it would help Dad out, and he won’t have to worry about it over the weekend.” Mom thought for a while and then decided to let下列过程不能引起基因重组的是 A．减数分裂时，同源染色体的非姐妹染色单体之间发生交换 B．减数分裂时，非同源染色体的自由组合 C．受精过程中，精子和卵细胞的结合 D．肺炎双球菌转化实验中，R型肺炎双球菌转化为S型肺炎双球菌