Answer:
Indolebutyric acid.
Step-by-step explanation:
The chemical coordination in case of plants occurs with the help of hormones and metabolites. Important hormones present in plants are auxins, gibberellins, cytokinin, ethylene and abscisic acid.
The indolebutyric acid is the important plant hormone that belongs to the auxin family. This is a white crystalline solid and yellow in color. The indolebutyric acid is used commercially for the plant rooting products. It promotes the rooting of the plant cutting.
Thus, the correct answer is option (c).