The correct option is A 2, 4- D
2, 4 - Dichlorophenoxyacetic acid is a common systemic herbicide used in the control of broadleaf weeds. It is one of the most widely used herbicides in the world. 2, 4 - D is a synthetic auxin and as such it is often used in laboratories for plant research and as supplement in plant cell culture media such as MS medium.