贯穿螺栓连接的母线两外侧均应有平垫圈，相邻螺栓垫圈间应有（）mm以上的净距。
A.1
B.3
C.5
D.8
参考答案：B
We won't be able to learn English well _____ we learn enough words by heart and do enough reading. [ ]
A. as
B. once
C. when
D. unless
经常小便淋漓不尽，伴神疲乏力气短，突然小便闭塞，小腹胀痛，舌淡，脉沉而无力，为
A．虚证转实B．热证转寒C．实证转虚D．因虚致实
