采煤机通过电气设备来实现的保护有失压保护和()。
A、漏电保护
B、牵引过零保护
C、超速保护
D、电机过热保护
E、差速保护
参考答案:B, C, D, E
图上距离一定,实际距离和比例尺成正比例.______.
The number of the students in our school _________ 600, but a number of students _________ living in the school.
A.is, like
B.is, likes
C.are , like
D.are, likes