动臂式起重机的起重量不变,减小工作幅度,起重量就可增加。
参考答案：对
The mother didn't know ______ to blame for the broken glass as it happened while she was out. [ ]
A. who
B. when
C. how
D. what
我国多地震灾害的原因是什么？怎样减轻地震所造成的危害？
