A plant hormone, which is primary regulator of abscission process is

✅ Explanation: Ethylene is a gaseous plant hormone that plays a key role in the abscission process, which is the shedding of leaves, flowers, or fruits from a plant. It promotes the breakdown of cell walls in the abscission zone, leading to the separation of the organ from the plant.

📌 Other Options Explanations:
Auxin: apical dominance
ABA (Abscisic Acid): ABA can promote abscission under certain conditions, also called stress hormone
Gibberellins: Gibberellins are involved in various growth processes, breaking dormancy is main function.