减数分裂过程中，染色体数目减半发生在 [ ]
A．精原细胞滋长增大时
B．精细胞变成精子时
C．第二次分裂结束时
D．第一次分裂结束时
答案：D
—Have you found the information about famous people you can use for the report.
—Not yet. I'll search some on the Internet. [ ]
A. that
B. who
C. what
D. Whom
tRNA转最后稀有碱基的生成不包括
A．甲基化反应B．脱氨反应C．还原反应D．转位反应E．脱羧反应
