## Core Concept
The question tests understanding of radioactive disintegration and the resulting products, specifically focusing on the production of a gaseous daughter element. Radioactive disintegration involves the decay of unstable atomic nuclei, leading to the emission of radiation and the formation of a more stable nucleus, which may be a different element.

## Why the Correct Answer is Right
The correct answer, , disintegrates into , which is a noble gas and therefore gaseous at room temperature. This process involves alpha decay, where an atomic nucleus emits an alpha particle (helium nucleus) to become a different element. For example, Radium (Ra) decays into Radon (Rn), which is a gas.

## Why Each Wrong Option is Incorrect
* **Option A:** does not directly decay into a gaseous element in a simple disintegration process relevant to common radioactive series.
* **Option B:** decays but into solid elements primarily.
* **Option D:** also does not directly result in a gaseous daughter product through simple radioactive decay relevant to the context.

## Clinical Pearl / High-Yield Fact
A key point to remember is that Radon gas, a product of Radium decay, is a significant concern in uranium mining due to its radioactive nature and potential to cause lung cancer. This highlights the importance of understanding radioactive decay series.

## Correct Answer: C.