The correct option is D Gamma rays
Mutation is the process by which genetic variations are created through changes in the nucleotide sequence within DNA. In a process known as mutational breeding, mutations are artificially induced in plants to obtain desirable characters. It can be achieved by chemicals or ionising radiations like gamma rays.
Infrared rays have energy lower than what is required to induce mutations.
Zeatin and kinetin are cytokinins, a type of plant growth regulators which have cell-division promoting activities. The are incapable of inducing mutations.