**Core Concept**
The question is testing the student's ability to distinguish between hyperplasia and adenomatous polyps, which are two distinct colonic mucosal lesions. Hyperplasia refers to an increase in the number of cells in a tissue without an increase in the size of the tissue, whereas adenomatous polyps are neoplastic lesions with potential for malignant transformation.

**Why the Correct Answer is Right**
To differentiate between hyperplasia and adenomatous polyps, one must assess the cellular architecture and the presence of cellular atypia. Adenomatous polyps exhibit a disordered glandular architecture and cellular atypia, including nuclear crowding, hyperchromasia, and increased mitotic activity. In contrast, hyperplastic polyps have a normal glandular architecture but may exhibit increased cellularity. Therefore, the key to distinguishing between these two lesions lies in the assessment of cellular atypia and glandular architecture. The correct answer is a procedure that allows for the evaluation of cellular morphology and atypia.

**Why Each Wrong Option is Incorrect**
**Option A:** Mucosal biopsy may not provide a representative sample of the polyp and may not allow for the evaluation of glandular architecture and cellular atypia.
**Option B:** Colonoscopy is a diagnostic tool that allows for the visualization of the polyp but does not provide information on cellular morphology and atypia.
**Option C:** CT scan is a radiological imaging modality that does not provide information on cellular morphology and atypia.

**Clinical Pearl / High-Yield Fact**
In the evaluation of colonic polyps, it is essential to assess the polyp's morphology and cellular architecture to determine its nature. Adenomatous polyps are neoplastic lesions with potential for malignant transformation, whereas hyperplastic polyps are generally considered to be non-neoplastic.

**Correct Answer:** D. Histopathological examination of the excised polyp.