船舶沟通与通信的障碍主要是:()
①物理障碍②人为障碍③语言障碍④地理障碍
A.①②③④
B.①②③
C.①②
D.①②④
参考答案:B
(2013·高考陕西卷)The children________lost in the woods;otherwise,they would have been at the lakeside camp as scheduled.
A.must have got
B.must get
C.should have got
D.should get
挖填方交界处,填土低于()的路堤都不应在冬期填筑。
A.1m
B.2m
C.3m
D.5m