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

Reference: https://docs.splunk.com/Documentation/Splunk/7.2.6/Search/Aboutsubsearches