**Core Concept**
The most commonly used material post pulpectomy is a type of filling material used to fill the root canal after the removal of the pulp tissue. This material is designed to prevent bacterial contamination, promote healing, and provide a foundation for the permanent restoration of the tooth.

**Why the Correct Answer is Right**
The correct answer is zinc oxide-eugenol (ZOE) due to its antimicrobial properties and ability to promote healing. ZOE is a mixture of zinc oxide powder and eugenol liquid, which creates a seal in the root canal and helps to prevent bacterial growth. The eugenol in ZOE also has analgesic and anti-inflammatory properties, which can help to reduce pain and inflammation in the surrounding tissues. The use of ZOE as a pulpal dressing is a common practice in endodontics, as it provides a safe and effective way to fill the root canal and promote healing.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect as it does not specify a commonly used material post pulpectomy. While there are many materials used in endodontics, ZOE is the most commonly used material for this purpose.
* **Option B:** This option is incorrect as it is not a suitable material for use in the root canal. Materials such as gutta-percha are used for obturation, not as a pulpal dressing.
* **Option C:** This option is incorrect as it is not a commonly used material post pulpectomy. While some materials may be used for temporary restoration, they are not typically used as a pulpal dressing.

**Clinical Pearl / High-Yield Fact**
One important thing to remember when using ZOE as a pulpal dressing is that it should be removed before the placement of a permanent restoration. This is because ZOE can interfere with the bonding of the restoration to the tooth, leading to a poor seal and potentially causing further problems.

**Correct Answer:** C. Zinc oxide-eugenol (ZOE).