采煤工作面移动刮板输送机时，必须有（）的安全措施。
A、防止冒顶
B、防止顶伤人员
C、防止损坏设备
D、防止输送机弯曲
参考答案：A, B, C
The railway bridge ___________ by 2015 will provide a faster route to transport goods．
A．to be completed
B．is completed
C．completed
D．being completed
区域体层，系指照射角应小于（）
A.5°
B.10°
C.15°
D.20°
E.30°
