Answer:
OD) The singular form of 'caves' must be 'café' or 'cavis.'
Explanation:
The singular form of caves must be cave, as café or cavi mean totally different things. OA is true, as we have the examples of data, trivia, among others,
OC also true, as we have the examples of cactus – cacti  and focus – foci, and OB is true as well, as we can defer by analysis – analyses , ellipsis – ellipses.