For the treatment of deep seated tumors, the following rays are used.

Ans. is 'a' i.e. X-rays and Gamma-rays X-rays and gamma rays are electromagnetic waves with highest penetrating power.For deep seated tumours rays with maximum penetrating power is required so x-rays and gamma rays are used.Harrison 141h/e states - "Megavoltage X-rays are used to irradiate internal deep seated lesions since high energy penetrating beams deliver a less intense superficial dose and spares the skin".