**Core Concept**
Adipocere formation is a process of decomposition where fatty tissues in the body break down into a soap-like substance, typically in a humid environment. This process involves the action of bacteria and enzymes on the triglycerides in adipose tissue.

**Why the Correct Answer is Right**
Adipocere formation occurs when the body's natural processes are disrupted, leading to the breakdown of triglycerides into glycerol and fatty acids. These compounds are then acted upon by bacteria, such as Clostridium, which produce enzymes that break down the fatty acids into soap-like substances. This process is often seen in cases of drowning or prolonged exposure to water, where the body's tissues are subjected to a humid environment.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because adipocere formation does not typically occur in dry environments. The presence of moisture is essential for the breakdown of triglycerides into glycerol and fatty acids, which are then acted upon by bacteria.
**Option B:** This option is incorrect because adipocere formation is not a process that occurs immediately after death. It typically takes several days to weeks for the process to occur, depending on the environmental conditions.
**Option C:** This option is incorrect because adipocere formation is not a process that is exclusive to certain parts of the body. Fatty tissues throughout the body can break down into soap-like substances, not just in specific areas such as the face or extremities.

**Clinical Pearl / High-Yield Fact**
One important fact to remember is that adipocere formation can be a significant diagnostic clue in cases of drowning or prolonged exposure to water, as it can help forensic pathologists reconstruct the circumstances surrounding the death.

**Correct Answer:** D.