四肢血管正常的多普勒频谱波形是（）。 A.单相波 B.双相波和单

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问题单项选择题 A型题

四肢血管正常的多普勒频谱波形是（）。

A.单相波

B.双相波和单相波

C.双相波

D.三相波

E.单相波和三相波

答案

参考答案：D

解析：四肢血管正常的多普勒频谱波形是三相波。

选择题

--- Why do you often take exercise? --- _____ me keep fit.

A．Help

B．Helping

C．To help

D．helped

选择题

In the early morning, all of us stood at the top of the mountain to ________ east of the city, watching ________ burning sun rising.

A．the; a

B．/; a

C．the; the

D．the;/