Which of the Following Searches Would Return Events with Failure

Multiple Choice

Which of the following searches would return events with failure in index netfw or warn or critical netops ?

A) (index=netfw failure) AND index=netops warn OR critical
B) (index=netfw failure) OR (index=netops (warn OR critical) )
C) (index=netfw failure) AND (index=netops (warn OR critical) )
D) (index=netfw failure) OR index=netops OR (warn OR critical)