**Core Concept**
The earliest manifestation of cell injury is a critical concept in understanding cellular pathophysiology. It refers to the initial changes that occur within cells when they are exposed to stress, toxins, or damage, ultimately leading to cell death or dysfunction. This process involves complex interactions between various cellular components, including proteins, membranes, and organelles.

**Why the Correct Answer is Right**
The correct answer is related to the concept of cellular swelling, which is the earliest and most non-specific sign of cell injury. This occurs due to an influx of ions and water into the cell, leading to an increase in cell volume. The sodium-potassium pump (Na+/K+-ATPase) is responsible for maintaining the ionic balance across the cell membrane. When the pump is overwhelmed or damaged, sodium ions enter the cell, leading to cellular swelling. This process is often reversible, but if left unchecked, it can progress to more severe forms of cell injury.

**Why Each Wrong Option is Incorrect**
**Option A:** Cellular depolarization is a consequence of cell injury, but it is not the earliest manifestation. Depolarization occurs when the cell membrane potential is disrupted, leading to an influx of calcium ions and activation of various cellular processes.

**Option B:** Loss of mitochondrial membrane potential is a hallmark of cell injury, but it occurs later than cellular swelling. Mitochondrial dysfunction is a critical event in the progression of cell injury, but it is not the initial sign.

**Option C:** Apoptosis is a form of programmed cell death, which is a late event in cell injury. Apoptosis is a complex process involving multiple cellular pathways, but it is not the earliest manifestation of cell injury.

**Clinical Pearl / High-Yield Fact**
Remember that cellular swelling is the earliest and most non-specific sign of cell injury, and it can occur in response to various forms of cellular stress, including ischemia, toxins, and infections. Early recognition of cellular swelling is crucial in preventing further cell damage and promoting recovery.

**Correct Answer: C. Loss of mitochondrial membrane potential is a hallmark of cell injury, but it occurs later than cellular swelling. Apoptosis is a form of programmed cell death, which is a late event in cell injury.