The man we followed suddenly stopped and looked as if       whether he was going in the right direction. [ ]

A. seeing

B. having seen

C. to have seen

D. to see

35岁经产妇，孕35周，双胎分娩两个男婴后检查，一个胎盘及一个羊膜囊，试问受精卵分裂及复制发生在受精后

A．第7～8天

B．第1～2天

C．第3～4天

D．第5～6天

E．第9～13天