单项选择题
The points on the earth’s surface where the magnetic dip is 90° are（）.
A.Along the magnetic equator B.Connected by the isoclinal line C.The isopors D.The magnetic poles
单项选择题 The four standard light colors used for lighted aids to navigation are red，green，white，and （）.
单项选择题 The equator is（）.
单项选择题 Restricted areas at locks and dams are indicated by（）.
