**Core Concept**
The scenario describes a dental restoration procedure involving the exposure of mesiobuccal pulpal horns in a primary maxillary first molar with a moderate caries lesion on the mesial and distal surfaces. This situation requires careful consideration of the treatment approach to ensure the preservation of the tooth structure and the pulp vitality.

**Why the Correct Answer is Right**
In cases of mechanical exposure of pulpal horns, the primary concern is to prevent further irritation and potential damage to the pulp. The correct treatment approach is to perform a direct pulp cap (DPC) or a pulp capping procedure. This involves applying a biocompatible material, such as calcium hydroxide or a modern pulp capping agent, over the exposed pulp to promote the formation of a hard tissue barrier and reduce inflammation. The goal is to preserve the pulp vitality and allow the tooth to continue functioning.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is not specified, but it may suggest further caries removal or a more extensive restoration procedure. However, in the case of pulpal horn exposure, aggressive caries removal or extensive restorative procedures can further irritate the pulp and lead to pulpal necrosis.
* **Option B:** This option is not specified, but it may suggest a more conservative approach, such as a partial pulpotomy or a pulpectomy. However, in cases of pulpal horn exposure without signs of pulpal necrosis, these procedures may not be necessary and can compromise the tooth's vitality.
* **Option C:** This option is not specified, but it may suggest a more aggressive approach, such as a full pulpotomy or a pulpectomy. However, in cases of pulpal horn exposure without signs of pulpal necrosis, these procedures may not be necessary and can compromise the tooth's vitality.

**Clinical Pearl / High-Yield Fact**
In cases of pulpal horn exposure, it's essential to consider the tooth's age, the extent of caries, and the presence of any signs of pulpal necrosis before deciding on a treatment approach. A direct pulp cap or pulp capping procedure can be an effective way to preserve the pulp vitality and allow the tooth to continue functioning.

**Correct Answer:** C.