某二倍体动物的某细胞内含10条染色体，20个DNA分子，光学显微镜下观察到该细胞开始缢裂，则该细胞可能正在[ ]

A．进行有丝分裂

B．进行基因的自由组合

C．产生精子

D．进行着丝粒分裂

A continuous sounding of a fog-signal apparatus indicates（）.

A.the vessel is in distress

B.the vessel has completed loading dangerous cargo

C.it is safe to pass

D.the vessel is anchored