下列实验基本操作正确的是[ ]
A.
B.
C.
D.
答案:B
—Maria, we are _____ apples, could you go and buy some?
—Sure. [ ]
A. short for
B. ready for
C. short of
目前,国内排水暗管、暗沟有多种结构形式,经试验比较成功的形式有哪些?