出灰用的工具，使用前应（）是否完整、牢固，用后应放在一定的地方。
A.检验；
B.检查；
C.查看。
参考答案：B
Statistics show that men have _____ as women do for every mile they drive．
A．serious accidents as twice many
B．twice as many serious accidents
C．twice serious accidents as many
D．serious accidents as many twice
只有两个通道的自动驾驶仪不包括：（）.
A.俯仰通道
B.副翼通道
C.升降舵通道
D.方向舵通道
