**Core Concept**
The scalpel blade used in intraoral surgery must be carefully selected to minimize tissue trauma and ensure optimal visibility. Intraoral surgery requires a blade that is thin, sharp, and capable of precise cuts.

**Why the Correct Answer is Right**
The most commonly used scalpel blade for intraoral surgery is the **Number 15C**. This is because it has a curved, sharp edge that allows for precise incisions and minimal tissue trauma. The curved shape also helps to reduce the likelihood of accidental cuts to surrounding tissues. The **Number 15C** blade is specifically designed for intraoral procedures, such as tooth extractions and surgical incisions.

**Why Each Wrong Option is Incorrect**
**Option A:** Other scalpel blades, such as the **Number 10**, may be too broad and cause excessive tissue trauma. They are not suitable for intraoral surgery.
**Option B:** The **Number 20** blade is too long and may be difficult to maneuver in the oral cavity. It is not the best choice for intraoral procedures.
**Option C:** The **Number 12** blade is too short and may not provide enough leverage for precise incisions. It is not the most commonly used blade for intraoral surgery.

**Clinical Pearl / High-Yield Fact**
When selecting a scalpel blade for intraoral surgery, it is essential to consider the specific requirements of the procedure. A sharp, thin blade with a curved edge, such as the **Number 15C**, is ideal for minimizing tissue trauma and ensuring optimal visibility.

**Correct Answer: D. Number 15C blade**