Okay, let's tackle this question. The user is asking about a complete denture patient with genial tubercles at the level of the mandibular ridge crest. The question is about the denture base's positioning. First, I need to recall the anatomy of the mandible. Genial tubercles are bony prominences on the lingual aspect of the mandible, usually located below the crest of the ridge. If they're at the level of the crest, this might affect denture fit.

The core concept here is understanding the normal anatomy of the mandible and how anatomical variations impact denture design. Genial tubercles being at the crest could mean there's less undercut for retention. Normally, the denture base would extend to the retromolar pad, but if the genial tubercles are higher, maybe the denture can't extend as far, leading to poor retention. So the correct answer would relate to the denture base not reaching the retromolar pad.

Now, looking at the options (even though they're not listed), the correct answer should state that the denture base cannot extend to the retromolar pad. The other options might suggest incorrect adjustments, like increasing pressure or altering the occlusal plane, which aren't appropriate here. The key is that the genial tubercles' position limits the denture's extension, affecting retention and stability. The clinical pearl is remembering that anatomical landmarks like genial tubercles must be considered for proper denture fit.

**Core Concept**
The genial tubercles are bony prominences on the lingual surface of the mandible. In complete denture construction, the denture base's extension and retention depend on anatomical landmarks like the genial tubercles and retromolar pad. If genial tubercles are at the level of the mandibular ridge crest, they limit the denture base's posterior extension.

**Why the Correct Answer is Right**
When genial tubercles are at the level of the crest, the denture base cannot extend posteriorly beyond the retromolar pad. This reduces the available undercut for retention, leading to decreased stability. Proper denture design must account for the genial tubercles' position to avoid tissue irritation or improper load distribution. The retromolar pad provides primary retention, but its accessibility is compromised if the genial tubercles are elevated.

**Why Each Wrong Option is Incorrect**
**Option A:** Suggests the denture base can extend to the retromolar pad. This is incorrect because elevated genial tubercles physically block posterior extension.
**Option B:** Claims the denture base should be thickened over the genial tubercles. Thickening increases pressure and risks mucosal ulceration.
**Option C:** Proposes altering the occlusal plane to avoid the genial tubercles. This would compromise occlusal balance and chewing efficiency.

**Clinical Pearl / High-Yield Fact**
Always assess genial tubercles' position during preliminary impressions. If they are at or above the ridge crest, the denture base must be contoured to avoid impingement, and retention strategies should focus on anterior regions or the buccal shelf.

**Correct Answer: C. The denture base cannot extend posteriorly beyond the retromolar pad**

✓ Correct Answer: D. Should cover them and relief is must