## Core Concept
The core concept being tested here is the generation of X-rays, specifically the material used as the target in an X-ray tube. X-rays are generated when high-energy electrons collide with a metal target, causing deceleration and emission of X-ray photons.

## Why the Correct Answer is Right
The correct answer, Tungsten (W), is used as the target material in X-ray tubes because of its high atomic number (Z=74) and high melting point (3422°C). When high-energy electrons collide with the Tungsten target, they are rapidly decelerated, producing X-rays through the bremsstrahlung process. This process is efficient due to Tungsten's high atomic number, which allows for a higher probability of electron-nucleus interactions.

## Why Each Wrong Option is Incorrect
* **Option A: Molybdenum**: While Molybdenum is used in some X-ray tubes, particularly for mammography due to its characteristic X-rays, it is not the primary target material for general X-ray generation.
* **Option B: Rhodium**: Rhodium is sometimes used in combination with Molybdenum in mammography targets but is not the standard target material for generating X-rays.
* **Option D: Copper**: Copper is not typically used as a target material for X-ray generation. It has a lower atomic number (Z=29) and melting point compared to Tungsten, making it less efficient for X-ray production.

## Clinical Pearl / High-Yield Fact
A key point to remember is that the target material in an X-ray tube is typically made of Tungsten due to its optimal characteristics for X-ray production. This is crucial for understanding the principles of X-ray generation in radiology.

## Correct Answer: C. Tungsten.