**Core Concept**
Drowning is a significant cause of accidental death worldwide, and its diagnosis can be challenging. Anti-mortem drowning refers to drowning that occurs before death, whereas post-mortem drowning occurs after death. The key feature that distinguishes anti-mortem from post-mortem drowning is the presence of water in the lungs.

**Why the Correct Answer is Right**
The feature indicative of anti-moem (anti-mortem) drowning is the presence of water in the lungs, which is due to the aspiration of water while the person is still alive. This is often accompanied by the presence of aquatic plants, dirt, or other foreign particles in the lungs, which are inhaled along with water. The lungs also show signs of congestion and edema, indicating that the person was still alive when they inhaled the water.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not specify the presence of water in the lungs, which is a key feature of anti-moem drowning.
**Option B:** This option is incorrect because it refers to post-mortem changes, which are not indicative of anti-moem drowning.
**Option C:** This option is incorrect because it is a feature of post-mortem drowning, not anti-moem drowning.

**Clinical Pearl / High-Yield Fact**
The presence of water in the lungs and the presence of aquatic plants or foreign particles are key features that distinguish anti-moem from post-mortem drowning. These features should be looked for in forensic examinations to determine the cause of death.

**Correct Answer: B. Post-mortem changes such as putrefaction and gas bubbles in the lungs.