－ Did Linda see the traffic accident?

－ No, no sooner _____ impossible now does seem possible.[ ]

A. had she gone

B. she had gone

C. has she gone

D. she has gone

HEPA是指（）。

A.通风控制系统

B.高效空气过滤器

C.建筑物排风系统

D.标准操作规范