**Core Concept**
Semi-Smokeless black powder is a type of propellant used in firearms, consisting of a mixture of chemicals that undergo rapid combustion to produce a high-pressure gas. The composition of semi-smokeless black powder is critical in determining its performance and characteristics.

**Why the Correct Answer is Right**
Semi-smokeless black powder typically contains a mixture of charcoal, sulfur, and potassium nitrate (saltpeter). The potassium nitrate serves as the oxidizer, while the charcoal and sulfur provide fuel. When ignited, the mixture undergoes a rapid exothermic reaction, releasing gases that propel the projectile out of the firearm. The sulfur content helps to reduce the smoke produced during combustion.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not accurately represent the composition of semi-smokeless black powder. While charcoal is a component, the absence of sulfur and potassium nitrate would result in a different type of propellant.
**Option B:** This option is incorrect because it contains an incorrect combination of chemicals. The addition of aluminum, for example, would not be typical in semi-smokeless black powder.
**Option C:** This option is incorrect because it does not accurately represent the composition of semi-smokeless black powder. The inclusion of other chemicals, such as boron, would not be characteristic of this type of propellant.

**Clinical Pearl / High-Yield Fact**
It's essential to note that different types of propellants have varying properties and performance characteristics. Understanding the composition and behavior of semi-smokeless black powder is crucial for firearms enthusiasts and professionals.

**Correct Answer: C. Charcoal, sulfur, and potassium nitrate.**