单项选择题
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
River currents tend to（）.A.pick up speed where the chan...
单项选择题River currents tend to（）.
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
Priming of the tides occurs（）.A.at times of new and ful...
单项选择题Priming of the tides occurs（）.
A.at times of new and full Moon B.when the Earth，Moon，and Sun are lying approximately on the same line C.when the Moon is between first quarter and full and between third quarter and new D.when the Moon is between new and first quarter and between full and third quarter
One of the causes of ocean currents is density differen...
单项选择题One of the causes of ocean currents is density differences in the water. This is true because （）.
A.in an area of high density the water's surface is lower than in an area of low density B.surface water flows from an area of high density to one of low density C.the lesser the density gradient the freer the water is to move D.it is the density differences that cause the currents to stay in the troughs
