Even a mighty express train can be held up by signals. Which of the following words can be used to

replace “held up”? [ ]

A. delayed

B. slowed up

C. halted

D. retarded

当安装新的FMGC后，应该（）

A.检查导航数据库，按需更新导航数据库；

B.不需检查导航数据库；

C.不作任何检查。