Which of the following is a physical mutagen for induced mutagenesis in crop plants?

The correct option is A X-rays
Mutation breeding is an important technique in crop improvement. It uses either chemical mutagens or physical mutagen. Different kinds of radiations like X-rays, gamma rays UV rays, which cause mutations are called as physical mutagens. The electromagnetic radiations, like X-rays, penetrate tissues from a few millimetres to many centimetres. This results in mutations.
Few chemical mutagens are ethyl methane sulphonate (EMS), nitrous acid, nitrosoethyl urea, nitromethyl urea, sodium azide etc.