(A) That the exploration and subsequent mapping of the underwater cave system’s Byzantine interior requires extensive experience and caution has been proven both by the near-death experiences of amateur cave divers and by the massive costs of the rescue operations to save those amateur cave divers. - Wrong
should be "require", not "requires" - SV issue
(B) That the exploration and subsequent mapping of the underwater cave system’s Byzantine interior require extensive experience
...
should be "require", not "requires" - SV issue
(B) That the exploration and subsequent mapping of the underwater cave system’s Byzantine interior require extensive experience
...
