若事件A与B为互斥事件，且P(A)=0.3，P(A+B)=0.8，则P(B)等于( )，

A．0.3

B．0.4

C．0.5

D．0.6

His complaint about our management was not without reasons.

A. could be rectified


B. could be justified
C. was modified


D. could be enforced