采煤机的正确操作程序是什么？
参考答案：
检查、巡视→运转输送机→合隔离开关→供水→启动电动机→停止电动机→合离合器→启动采煤机→破煤→停机。
Cathy is taking notes of the grammatical rules in class at Sunshine School,where she ____ English
for a year. [ ]
A. studies
B. studied
C. is studying
D. has been studying
气缸盖螺栓预紧力大小均匀，可避免因（）而引起的疲劳断裂。
A．附加应力
B．机械应力
C．热应力
D．A+B+C
