关于周期性麻痹，下列哪项不对（）.
A.原因常不明
B.无肌张力增高
C.发作后可自行缓解
D.发作时血钾高
E.反射减弱
参考答案：D
Great changes ______ in the past few years, and a lot of factories ________.
A．had taken place; have been set up
B．have taken place; have been set up
C．took place; have set up
D．were taken place; were set up
系统发生振荡时，应争取在（）分钟内消除振荡，否则应在适当地点解列。
A、1～2
B、3～4
C、5～8
D、10
