适用于打钢板桩、钢管桩的桩锤是（)。A．振动桩锤B．单动气锤C．双动气锤D．柴油桩锤

Even earlier in __2__1000 B.C.

But an effect can become __2__a cause

this concept operated under common understood restrictions.

Broadly and simply putting, "culture" refers to a __2__

according to a report publishing recently by the Johns Hopking University.

a lake, about a hundred feet from the shore. There was a __2__

Astronomers and scientists think that a black hole is __2__a region of

for each state must, through legislative enactment or __2__executive proclamation

If he did __2__not care of his guest’s feelings

ancestors consume primarily a vegetable diet supplementing with animal foods __2__