I was going to take a photo of the world-famous painting when I noticed a__________ saying “No Photographing”.

A．signal

B．sign

C．sigh

D．spelling

环境有害因素对胚胎危害最严重的阶段（）。

A.妊娠16周内

B.妊娠8周内

C.妊娠12周内

D.妊娠28周内

E.妊娠37周内