_____ a reply, he decided to write again.

A．Not receiving

B．Receiving not

C．Not having received

D．Having not received

下列关于染色体组的说法，正确的是[ ]

A．21三体综合征患者体细胞中含有3个染色体组

B．四倍体水稻的单倍体体细胞中含2个染色体组

C．一个染色体组中的染色体大小、形态一般相同

D．雄蜂高度不育是因为体细胞中含1个染色体组