3级混凝土坝或浆砌石坝，坝高超过100m时，其级别可（）。
A.提高到2级
B.降低到4级
C.不变
D.提高到2级，但洪水标准可不提高
参考答案：D
If they will not accept a check, we shall have to pay in the cash, though it would be much trouble for both sides.
My father to Beijing. He hasn’t returned yet.
A. has gone B. has been C. went
