隐匿性传导可发生于()
A.房室交界区
B.窦房交界区
C.左、右束支
D.浦肯耶纤维
E.房室旁路
参考答案:A, B, C, D, E
--- Something wrong with my headache .
--- No wonder. You ___________ on the program for such a long time.
A.have worked
B.worked
C.have been working
D.were working
—It look like rain. Why not take ______ umbrella with you?
—Thank you. But I don't think it's necessary.[ ]
A. a
B. an
C. /
D. Several