Which one of the following generally act as an antagonist to gibberellins?

Correct option is C. ABA. Abscissic acid (ABA) is also called stress hormone. It is the mildly acidic hormone which functions as a general growth inhibitor by counteracting other hormones (Auxins, gibberellins, cytokinins) or reactions mediated by them. It causes stomatal closure, seed dormancy, and acts as an antagonist (opposite in function) to gibberellins as gibberellins promote seed germination. So, the correct answer is 'ABA'.