**Core Concept**
Reversible cell injury is characterized by cellular changes that can be restored once the cause of injury is removed. **Electron microscopy** can reveal these changes at the cellular level.

**Why the Correct Answer is Right**
In reversible cell injury, **electron microscopy** shows changes such as **cellular swelling**, **mitochondrial swelling**, and **dilatation of the endoplasmic reticulum**. However, the correct answer choice is not provided, so we will proceed with general information about reversible cell injury.

**Why Each Wrong Option is Incorrect**
**Option A:** Without the specific details of option A, we cannot provide a detailed explanation of why it is incorrect.
**Option B:** Similarly, without the details of option B, we cannot explain why it is wrong.
**Option C:** And option C's incorrectness cannot be specified without its content.
**Option D:** The same applies to option D.

**Clinical Pearl / High-Yield Fact**
A key point to remember is that reversible cell injury is characterized by changes that do not lead to cell death if the cause is removed promptly. **Cellular swelling** is one of the earliest signs of reversible cell injury.

**Correct Answer:** Correct Answer: C. Cellular swelling