單項(xiàng)選擇題

The agonic line on an isomagnetic chart indicates the （）.

A.magnetic equator
B.magnetic longitude reference line
C.points where there is no variation
D.points where there is no annual change in variation

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單項(xiàng)選擇題

Solid green arrows on the main body of a pilot chart indicate （）.

A.prevailing wind directions
B.prevailing ocean current directions
C.probable surface current flow
D.shortest great circle routes

單項(xiàng)選擇題

On the south and the east coasts of Block Island are circles with a dot in the center and labeled CUP. This is a （）.

A.conspicuous object
B.steep depression in the surrounding hills that resembles a cup
C.domed structure useful for navigation
D.calling-up-point used for traffic control