I'd choose D. I think "It is high time somebody did something" is a fixed expression.
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norwolfJack is a great talker. It’s high time that he ____ something instead of just talking. A will do B has done C do D didD is the only option possible out of the four. C is definitely ruled out as it should be He does, not He do.
norwolfIs 3# rare, in fact?It's time/high time he does someth
norwolfA will do B has done C do D didSo do I, but the examiners are probably looking for D, as mentioned above.
I think both C and D are correct