起重电磁铁壳体上,应有防止碰撞端子箱盖的保护措施。()
A、正确
B、错误
参考答案:A
I hear a number of workers in the factory_____out of work.
__Yes, and the number _____quite huge.
A.are; is
B.is; are
C.is; is
D.are; are
从激励的性质角度,可将激励分为()和()。