A.These temperature gradients tend in most cases to be impossible to describe mathematically.
B.The lower the contrast between the extremes of the gradient, the lower the resulting velocity of the jet stream.
C.Jet streams are responsible for most of the north-south transfer of heat between the equator and the poles.
D.The temperature gradient tends, on a non-negligible level, to augment the effects of the earth's rotation.
E.The gradient typically refers to differences in jet stream velocity at various longitudinal positions around the globe.
第4题
现代车辆发动机不论是汽油机还是柴油机广泛采用()。
A.铸铁活塞
B.铸钢活塞
C.低碳钢活塞
D.铝合金活塞
第8题
为减轻活塞的运动惯性,高速内燃机活塞采用()材料制造。
A.铸铁
B.铜合金
C.铝合金
D.尼龙
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