. —I have to get to the post office by six o’clock, but it is almost six now.

—        . This clock is fifteen minutes fast.

A．That’s too bad

B．Sounds good

C．Sure, you can

D．Take it easy

致畸因子作用于胚胎最敏感的时期是

A．受精后4～8周

B．孕5个月左右

C．受精后3～8天

D．受精后第3～8周末

E．受精时