**Core Concept:** The killing range of a military rifle refers to the maximum distance at which a bullet fired from a military rifle can reliably penetrate and cause fatal injury to a target. This depends on factors such as bullet type, caliber, velocity, and the anatomy and physiology of the target organism. In this scenario, we are considering a human target.

**Why the Correct Answer is Right:** The correct answer is **D**. The killing range of a military rifle depends on the bullet's kinetic energy, which is directly proportional to its mass and velocity squared. Bullet types like armor-piercing or high-velocity rounds can extend the killing range. However, the human body's defensive mechanisms also play a role.

At a relatively close range (around 100-200 meters), the bullet can enter the body and exit through the opposite side, causing significant damage to vital organs like the heart, lungs, or brain. The exit wound would often be larger than the entry wound, leading to extensive hemorrhage and death.

**Why Each Wrong Option is Incorrect:**

A. At a very close range (within a few meters), the kinetic energy and penetration capabilities of a bullet are sufficient to cause fatal injuries, making this option incorrect due to the extreme proximity.

B. Bullet velocity primarily affects the penetration depth but not necessarily the killing range. While higher velocity can increase the penetration depth, it does not make the bullet more likely to cause fatal injuries at greater distances.

C. Bullet type, such as armor-piercing or soft-point, affects penetration depth but not the overall killing range. The bullet's ability to cause fatal injuries depends on multiple factors, including velocity, mass, and the target's anatomy rather than bullet type alone.

**Clinical Pearls:** In military conflicts, the killing range of a military rifle is determined by a combination of bullet properties and target physiology. However, the lethal effects depend on factors like bullet velocity, mass, and the target's anatomy, not just bullet type. The entry and exit wounds, as well as their relative sizes, can help assess the severity of the injury. Understanding these concepts ensures safe handling of firearms and can aid in forensic investigations regarding firearm-related incidents.