**Core Concept**
Smokeless gunpowder, also known as modern gunpowder, is a type of propellant used in firearms. When ignited, it undergoes a rapid decomposition reaction, producing a large volume of gases. This process is crucial in propelling a bullet out of the barrel. Understanding the volume of gases produced by a given amount of smokeless gunpowder is essential in forensic medicine for calculating the velocity and trajectory of projectiles.

**Why the Correct Answer is Right**
The correct answer, **12,000-13,000 cc of gas**, is based on the explosive decomposition reaction of smokeless gunpowder. When one gram of smokeless gunpowder is ignited, it produces approximately 12,000-13,000 cubic centimeters (cc) of gas. This reaction is characterized by the rapid oxidation of the propellant's constituents, resulting in the production of a large volume of gases. The specific volume of gas produced depends on the type and composition of the smokeless gunpowder.

**Why Each Wrong Option is Incorrect**
**Option A:** 3000-4000 cc of gas is significantly lower than the actual volume produced by one gram of smokeless gunpowder. This option might be based on an outdated or incorrect calculation.
**Option B:** 9000-10,000 cc of gas is still lower than the actual volume produced, but closer to the correct range. However, it is not within the accepted range for one gram of smokeless gunpowder.
**Option D:** 15,000-16,000 cc of gas is higher than the actual volume produced, but this option might be based on a misunderstanding of the decomposition reaction or an incorrect calculation.

**Clinical Pearl / High-Yield Fact**
In forensic medicine, it's essential to remember that the volume of gas produced by smokeless gunpowder can affect the velocity and trajectory of projectiles. This knowledge can be crucial in reconstructing crime scenes and determining the origin of bullets or other projectiles.

**✓ Correct Answer:** C. 12,000-13,000 cc of gas