A.when the moon is new or full
B.when the moon and sun have declination of the same name
C.only when the moon and sun are on the same sides of the earth
D.at the beginning of spring when the sun is over the equator
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A.at the start of spring，when the Sun is nearly over the equator
B.only when the Sun and Moon are on the same side of the Earth and nearly in line
C.when the Sun and Moon are at approximately 90°to each other as seen from the Earth
D.when the Sun，Moon，and Earth are nearly in line，in any order
A.have lows lower than normal and highs higher than normal
B.have lows higher than normal and highs lower than normal
C.are unpredictable
D.occur in the spring of the year
A.its velocity in knots
B.direction from which it flows
C.estimated current
D.direction toward which it flows
A.interruption of the normal current flow by the footing
B.elevating in mud-slide zones
C.penetrating rapidly through a hard crust into weaker soils
D.extracting legs from soils with high cohesion
A.pick up speed where the channel widens
B.run slower in the center of the channel
C.hug the inside of a bend
D.cause the greatest depth of water to be along the outside of a bend
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Priming of the tides occurs（）.
（）is not a type of tide.
Neap tides occur when the（）.
The set of the current is the（）.
You are anchoring in a river where the current is from one direction only.The best way to lay out two anchors is to have them（）.
The tide（）.It’s 2 hours before low water，and（）your present position you will be aground at low water.
The two most effective generating forces of surface ocean currents are（）.
Water may boil up around the stern of a vessel in a channel due to（）.
When daylight savings time is kept，the time of tide and current calculations must be adjusted.One way of doing this is to（）.
The steady current circling the globe at about 60°S is the（）.