**Core Concept**
Somatic death, also known as clinical death, is a state where the body's physiological functions have ceased due to a lack of oxygen and nutrients, leading to cellular death. This concept is crucial in understanding the transition from life to death.

**Why the Correct Answer is Right**
Somatic death is characterized by the irreversible cessation of vital functions, including **circulation**. The body's inability to maintain circulation leads to a cascade of events, including tissue hypoxia, acidosis, and ultimately, cellular death. The other options, while related to the dying process, are not the primary indicator of somatic death. **Cessation of spontaneous respiration** (option b) can occur before somatic death, and **cooling of the body** (option a) is a post-mortem change. **Flat isoelectric E.E.G.** (option d) is a sign of brain death, which is a separate entity from somatic death. **Deep unconsciousness with no response to external stimuli or internal need** (option e) is a characteristic of brain death.

**Why Each Wrong Option is Incorrect**
**Option A:** Cooling of the body is a post-mortem change that occurs after somatic death, not a characteristic of it.

**Option B:** While cessation of spontaneous respiration is a sign of impending somatic death, it is not the definitive indicator.

**Option D:** Flat isoelectric E.E.G. is a sign of brain death, not somatic death.

**Option E:** Deep unconsciousness with no response to external stimuli or internal need is a characteristic of brain death, not somatic death.

**Clinical Pearl / High-Yield Fact**
It's essential to differentiate between somatic death and brain death, as they have distinct implications for organ donation and end-of-life care.

**Correct Answer:** C. Cessation of circulation