题目解析:
"可在第一句找到B的flat land,B正确,A虽然有说到,但不是沉积物沉积的地点,从from可以看出,所以要选的答案是A: The same thing happens to this day, though on a smaller scale, wherever a sediment-laden river or stream emerges from a mountain valley onto relatively flat land, dropping its load as the current slows.在第二句的前半句找到C和D,CD不正确: Sediments are also dropped where a river slows on entering a lake or the sea, the deposited sediments are on a lake floor or the seafloor at first..."