三相开关设备的额定频率标准值为()Hz。
A.45
B.50
C.55
D.60
参考答案:B
—Look! The trousers look so nice! Can I ?
—Of course.[ ]
A. try them on
B. try on them
C. try on it
D. try it on
如图所示,有关脊神经的组成哪项不对()
A.颈神经7对
B.胸神经12对
C.腰神经5对
D.骶神经5对
E.尾神经1对