A.low water slackB.high water slackC.high water ebbD.hi……

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

A.lower low water
B.high water
C.low water
D.sea level

单项选择题Clearance gauges at bridges indicate （）.

A.the height of the tide
B.depth of water under the bridge
C.charted vertical clearance at mean low water
D.distance from the water to low steel of the bridge

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

A.concealed
B.buried
C.existed
D.built

单项选择题Attention is called to the fact that in many cases charted depths may be decreased by up to （）.

A.one nautical mile
B.two kilometers
C.5 cables only
D.one fathom

单项选择题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 （）.

A.a vessel arrives at a port in a evening
B.a vessel leaves a port in a evening
C.a vessel arrives at a port in a morning
D.a vessel leaves a port in a morning