煤气管道应有一定坡度以利管内积水和焦油顺利流出。
参考答案:对
—Do you know who stole the computer?
—I don't know. But I'll try to ______ who did that. [ ]
A. hand out
B. look out
C. check out
D. find out
—Is this_______English car ?
— No, it’s______Japanese car.
A.a; a
B.a; an
C.an; an
D.an; a