The correct answer is (d) Abscisic acid.
Explanation: Abscisic acid is a plant hormone that is known to inhibit growth, while auxin, gibberellins, and cytokinins are all considered growth promoters.
Key points about the other options:
Auxin: Promotes cell elongation and plays a crucial role in apical dominance.
Gibberellins: Enhances stem elongation and can stimulate seed germination.
Cytokinins: Primarily responsible for cell division and promoting lateral bud development.