The correct option is A Auxin
Parthenocarpy is the process of development of fruits without the fertilization of ovules which leads to the formation of seedless fruits.
Treatment of young plants with auxin causes unpollinated ovaries in certain cultivars of strawberry, tomato, grape, and orange to produce the parthenocarpic fruit (seedless fruits).
Ethylene is a plant growth promoter as well as a plant growth inhibitor. It helps in the ripening of fruits.
Cytokinins are plant growth promoters that help in cell division in plants.
Gibberellins are plant growth promoters that help in germination of seeds and elongation of shoots.