下列举的各种细胞中,细胞核内基因成单存在的是( )
A:子房壁细胞
B:珠被细胞
C:受精卵
D:卵细胞
— This is a great chance that many people don't have.
— I see. I'll cherish(珍惜) it.
计算:(3a3)2=____.