The correct option is C gibberellin and cytokinin
Delay in leaf senescence is caused by gibberellin and cytokinin. They are also applied to vegetables to keep them fresh for a longer period. Leaf senescence is the last stage of the leaves when they become yellow and there is a lack of chlorophyll in these leaves.
Hormones like abscisic acid and ethylene promote leaf senescence.
Cytokinin helps to produce new leaves, chloroplast in leaves, lateral shoot growth and adventitious shoot formation.
Ethylene is a plant growth promoter as well as a plant growth inhibitor. It helps in the ripening of fruits.