-It's time ________. Good night.

-Good night. [ ]

A. to get up                    

B. to go to bed

C. get up                      

D. go to bed

在产品进行FMECA时，一般致命故障为( )严酷度。

A．Ⅱ类
B．Ⅲ类
C．Ⅳ类
D．Ⅰ类