**Core Concept**
Linear accelerators are medical devices used in radiation therapy to deliver high-energy radiation to cancerous cells. They work by accelerating electrons to high speeds, which then collide with a metal target to produce X-rays.

**Why the Correct Answer is Right**
The correct answer is X-rays, which are produced when high-speed electrons collide with a metal target in the linear accelerator. This process is called bremsstrahlung radiation. The energy of the X-rays is dependent on the energy of the electrons accelerated by the linear accelerator. The resulting X-rays have a broad spectrum of energies, making them suitable for treating various types of cancers.

**Why Each Wrong Option is Incorrect**
* **Option A:** Gamma rays are high-energy electromagnetic radiation produced by radioactive decay, not by linear accelerators.
* **Option B:** Neutrons are subatomic particles with no charge, which can be produced by some types of radiation therapy, but not by linear accelerators.
* **Option D:** Ultraviolet (UV) light is a form of electromagnetic radiation with lower energy than X-rays, not produced by linear accelerators.

**Clinical Pearl / High-Yield Fact**
Linear accelerators can produce X-rays with energies ranging from a few hundred kiloelectronvolts to several million electronvolts, making them versatile tools in radiation therapy.

**Correct Answer:** C. X-rays.