**Core Concept**
Pleomorphic adenoma, also known as a benign mixed tumor, is a common type of salivary gland tumor that arises from the epithelial cells of the salivary gland. It is characterized by its ability to exhibit a wide range of histological features, including both epithelial and connective tissue elements.

**Why the Correct Answer is Right**
Pleomorphic adenoma arises from the ductal epithelial cells of the salivary gland, specifically from the myoepithelial cells and the luminal epithelial cells. The tumor's growth is often driven by the abnormal proliferation of these cells, leading to the formation of a mixed tumor that contains both epithelial and connective tissue components. The presence of myoepithelial cells and the expression of specific markers such as S-100 protein and cytokeratins are characteristic features of pleomorphic adenoma.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because pleomorphic adenoma does not arise from the connective tissue of the salivary gland, but rather from the epithelial cells.
**Option B:** This option is incorrect because Warthin's tumor is a different type of salivary gland tumor that arises from the ductal epithelial cells, but it is characterized by its association with smoking and the presence of oncocytic cells.
**Option C:** This option is incorrect because basal cell adenoma is a different type of salivary gland tumor that arises from the myoepithelial cells, but it is characterized by its distinct histological features and lack of pleomorphism.

**Clinical Pearl / High-Yield Fact**
Pleomorphic adenoma is the most common type of salivary gland tumor, accounting for approximately 60-70% of all salivary gland tumors. It is often found in the parotid gland and can grow to a large size before causing symptoms.

**Correct Answer: D. Ductal epithelial cells of the salivary gland.**