在迷宫密封中，气体流过齿缝后进入两个密齿形成的较大的空腔后（）。

A、容积突然加大，形成很强的旋涡

B、流速降低

C、动能由于旋涡变为热量

D、压力回升很少

I had travelled only two hours one day ______ the winds increased so much that I had to put my

tent up _______ the winds became too strong. [ ]

A. when , before    

B. when , after    

C. when, until  

D. until , before