Last month, the Japanese government expressed their thanks for the aid they ________ from China.[ ]

A. receive  

B. are receiving

C. have received  

D. had received

对于原发性下肢深静脉瓣膜功能不全的检查最可靠的是（）。

A.超声多普勒检查

B.下肢活动静脉压测定

C.下肢深静脉造影

D.Perthes试验

E.Trendelenburg试验