题目

下列细胞中一定不存在同源染色体的是（ ） A． 小麦根尖细胞                        B． 受精卵 C． 初级精母细胞                        D． 小鼠的次级精母细胞 答案：DThere are some health problems that, when ___in time, can become bagger ones later on. A.not treated　 B. not being treated　 C. not to be treated　 D. not having been treated