单项选择题
Single Choice
库区淤积主要是河水进入水库后流速减小,泥沙随着河水运移过程中逐渐沉积,一般来讲,从上游到下游沉积的泥沙颗粒尺寸的变化是()?
The siltation in the reservoir area is mainly due to the decrease of the flow velocity after the river enters the reservoir. The sediment gradually deposits as the river moves. Generally speaking, the change in the size of the sediment particles from the upstream to the downstream is
A.逐渐增大 Gradually increase
B.逐渐减小 Gradually increase
C.大小均一 Uniform size
D.无法判断 Unable to judge