下列哪种方法适用于病毒的分离（）

A.过滤

B.超速离心

C.透析

D.细胞或动物接种和传代

E.亲和层析

The fire spread through the hotel very quickly but everyone __________ get out.  [ ]

A. had to  

B. would  

C. could  

D. was able to