-Be careful! You might fall into the water.

-Thank you. I____.I______ so close to the pool.

A．didn't know; am standing

B．don't know; am standing

C．didn’t know; was standing

D．didn't know;Would stand

患者，女性，45岁。左侧小腿表浅静脉曲张5年，长时间站立后小腿和足部有胀痛。足靴区皮肤增厚粗糙，伴色素沉着。顺行性静脉造影显示大隐静脉显著扩张，深静脉通畅、呈直筒状。

该患者接受逆行性静脉造影检查，发现造影剂自股骨头平面逆流至膝关节平面，则其瓣膜功能属于（）.

A.0级

B.3级

C.2级

D.4级

E.1级