Which of the following chemical is being commercially used in India to increase the size and length of the bunch of grapes?

The correct option is B Gibberellins

• Gibberellic acid is the most common GA used commercially. It can be readily obtained in large quantities from fermentations of the fungus Gibberella fujikori.
• Almost all seedless grapes on the market are treated with GA${}_3$. It substitutes for the presence of seeds, which would normally be the source of native GAs for fruit growth.
• Repeated spraying with GA${}_3$ increases both rachis length and fruit size. The increased rachis length prevents the cluster from being too compact, and this reduces the chance of fungal growth inside the cluster.

So, the correct answer is option B.