限制型心肌病最常见的心律失常为（）。
A.室上速
B.室速
C.房颤
D.房室传导阻滞
E.病窦
参考答案：C
He collected information on 1,000 people, whose IQ when they were ten years old. [ ]
A. is tested
B. has tested
C. would test
D. had been tested
过抛物线y2=8x的焦点的弦AB以（4，a）为中点，则|AB|=______．
