Mr. Smith asked Jenny some new words and let her to               on the blackboard.[ ]

A. write them down            

B. write it down  

C. write down it                

D. write down them

禁止（）进入高原铁路。

A.棚车

B.制动故障关门车

C.踏面擦伤车

D.二个月内到期的铁路货车