Heriditary variation in plants have been produced by the use of

Answer: Option D

Hereditary variations in plants have been produced by the use of Gama ray, while others in options like, auxin, gibberellic acid and DDT are hormones and pesticides.
Gamma radiation (GR) is one of the most widely used mutagenic agents in plants because it is reported to induce high genetic variability.
This type of radiation can be generated by radioisotopes such as carbon-14 (¹⁴C), cobalt-60 (⁶⁰Co), cesium-137 (¹³⁷Cs) and plutonium-239 (²³⁹Pu).