Which of the following has been used to induce hereditary changes in plants?

Explanation

Hereditary variations in plants can be generated using various agents. While X-rays (option B) and chemical agents can cause mutations, gibberellic acid (option C) is a plant hormone known to influence growth and development, and it has been utilized to induce genetic variations in plants. DDT is an insecticide and auxins are growth regulators but not primarily used for hereditary variation induction.