两根等高避雷针之间的距离与针高之比不宜大于（）。
A.1
B.3
C.5
D.6
参考答案：C
Something ________ otherwise he ________ here then. [ ]
A. must happen; would have been
B. must have happened; would be
C. must have happened; would have been
D. would happen; would be
城市燃气管道按设计压力分为（）级。
A.3
B.5
C.6
D.7
