The distance between any two meridians measured along a parallel of latitude and expressed in miles is the （）.

Clearances of bridges and overhead cables below Bonneville Dam refer to heights in feet above mean （）.

As these features are not all charted，special caution should be exercised （） vessels navigating in the vicinity.

The meaning of ebb tide is that （）.

During a period of whiteout，you should expect which of the following（）.

At last，the palm trees that fringe the natural harbor of Port Aloahoa come into view on the horizon lit by the setting sun.The meaning of this sentence is that （）.

Information on the operating times and characteristics of foreign radiobeacons can be found in which publication? （）

Attention is called to the fact that in many cases pipelines are not （） and charted depths may be decreased by up to 2 meters．

The height of eye correction is smaller than geometrical dip because of （）.

AFTER DROPPING THE PILOT means （）.