**Core Concept**
The management of a tooth with acute pulpal abscess requires careful consideration of the irrigant used to prevent further irritation and promote healing. The choice of irrigant depends on its antimicrobial properties, pH level, and ability to dissolve organic material.

**Why the Correct Answer is Right**
The correct answer is **C. Normal Saline**. Normal saline is used during the opening of a tooth with acute pulpal abscess because it is isotonic and non-irritating, making it ideal for rinsing the infected area. Its pH level is close to neutral, which helps maintain the health of the surrounding tissues. Additionally, normal saline does not contain any antimicrobial agents that could interfere with the treatment plan.

**Why Each Wrong Option is Incorrect**
* **Option A:** **Hypochlorite solution** is too harsh and can cause further irritation to the infected area. Its alkaline pH can also damage the surrounding tissues.
* **Option B:** **Chlorhexidine** is a disinfectant that is not suitable for use in the oral cavity due to its potential for causing mucosal irritation and altering the oral flora.
* **Option D:** **Ethanol** is not suitable for use in the oral cavity due to its potential for causing mucosal irritation and altering the oral flora.

**Clinical Pearl / High-Yield Fact**
When managing a tooth with acute pulpal abscess, it is essential to use a gentle and non-irritating irrigant to promote healing and prevent further complications.

**Correct Answer: C. Normal Saline**