–You’ve left the window open.

–______. I’ll go and close it.

A．So I have

B．So have I

C．So I did

D．So did I

下肢静脉的静脉瓣功能不全，观察有无返流及其速度快慢时，应首选下述哪种技术？( )

A．M型

B．B超

C．能量图

D．彩色多普勒血流显像

E．三维超声