My father was reading a book ________ I was doing my homework.
A:before
B:after
C:when
D:while
写出下列词语的近义词
吩咐____ 完整____
茂盛____ 姿态____
玉米体细胞中有20条染色体,经两次分裂后,形成的子细胞所含有的染色体数目是