The correct option is (b) cytokinins.
Explanation:
Ratio of cytokinin to auxin controls cell differentiation. If there is more cytokinin than auxin, shoot buds develop. Relatively more auxin than cytokinins leads to the development of roots. Abscisic Acid (ABA) rs known as natural plant growth inhibitor. Gibberellin stimulates stem elongation, leaf expansion, bolting, flowering, etc, Ethylene is a fruit ripening hormone.
