**Core Concept**
The maxillary impression is a crucial step in the fabrication of complete dentures for edentulous patients. To record the correct impression, the patient must be positioned in a way that allows the dentist to capture the accurate shape and size of the maxillary arch. This involves manipulating the patient's mandible to achieve the optimal position for impression recording.

**Why the Correct Answer is Right**
The movement of the mandible from side to side, also known as lateral mandibular movement, is essential to record the correct impression. This movement helps to capture the correct width and shape of the maxillary arch, taking into account the anatomical variations in the maxillary tuberosity and the surrounding soft tissues. By recording the impression with the mandible in this position, the dentist can ensure an accurate fit of the denture.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because it does not describe the correct movement of the mandible during maxillary impression recording.
* **Option B:** This option is incorrect because it does not provide a clear description of the movement required to record the maxillary impression.
* **Option D:** This option is incorrect because it does not take into account the anatomical variations that occur during lateral mandibular movement.

**Clinical Pearl / High-Yield Fact**
To record an accurate maxillary impression, the patient should be instructed to move their mandible from side to side, allowing the dentist to capture the correct shape and size of the maxillary arch.

**Correct Answer: C.**