单项选择题
A.prevailing wind directions B.prevailing ocean current directions C.probable surface current flow D.shortest great circle routes
On the south and the east coasts of Block Island are ci...
单项选择题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
Navigational charts are （） frequent changes，the importa...
单项选择题Navigational charts are （） frequent changes，the important one of which are promulgated by Admiralty Notices to Mariners．
A.published with B.combined with C.in connection with D.subject to
My position has been obtained （） astronomical observati...
单项选择题My position has been obtained （） astronomical observation．
A.with B.from C.on D.by
