洁净厂房内洁净室和疏散走道的顶棚的耐火极限分别不应低于( )A.0.25h和1.0h B.0.

洁净厂房内洁净室和疏散走道的顶棚的耐火极限分别不应低于( )

A.0.25h和1.0h

B.0.4h和1.0h

C.0.5h和0.5h

D.1.0h和0.5h