Astronauts in a spaceship have to _______weightless conditions _______are quite different from ______ on the earth.      [ ]

A. do with; which; those  

B. deal with; that; that  

C. face; which; those  

D. solve; where; what

急性呼吸窘迫综合征时形成肺水肿的主要机制是（）。

A.微血管内静水压升高

B.肺血管收缩致肺动脉压升高

C.肺淋巴回流障碍

D.血液胶体渗透压降低

E.肺泡一毛细血管膜损伤致通透性