Which of the following statements is/are correct?

(a) Microwaves are produced by klystron valves.

(b) Radio waves are produced by inner shell electrons when they move from one energy level to a lower energy level.

Correct option is D

Klystron valves are used to amplify high-frequency microwaves. These devices are capable of producing microwave frequencies and are commonly used in applications such as radar, satellite communication, and microwave ovens.