《顶板管理办法》规定：井下所有锚杆初锚力必须达到（）吨。
A、1
B、3
C、5
D、6
参考答案：C
Ping Pong is popular among China, _____ both young and old can _____. [ ]
A. about it; take part in
B. in it; take part
C. in which; take part in
D. in which; take part
电力安全注意事项应包括哪些内容？
