## Core Concept
The core concept being tested here is the difference between two histamine H2-receptor antagonists, ranitidine and cimetidine, which are used to reduce stomach acid production. These drugs work by competitively inhibiting histamine's action on H2 receptors in the parietal cells of the stomach.

## Why the Correct Answer is Right
Ranitidine and cimetidine are both H2 receptor antagonists but they have distinct differences in terms of their potency, side effects, and drug interactions. The primary difference lies in their potency and side effect profile. Ranitidine is more potent and has fewer side effects compared to cimetidine. Specifically, cimetidine has anti-androgenic effects leading to gynecomastia and impotence, which are not commonly seen with ranitidine.

## Why Each Wrong Option is Incorrect
- **Option A:** This option is incorrect because while both drugs do have effects on the stomach, the specificity of their difference is not clearly defined here.
- **Option B:** This option does not provide a clear, accurate distinction between the two drugs.
- **Option C:** This option correctly identifies that one of the significant differences between ranitidine and cimetidine is their side effect profile, particularly that cimetidine can cause anti-androgenic effects like gynecomastia.
- **Option D:** This option is incorrect as it does not accurately represent a well-known difference between the two drugs.

## Clinical Pearl / High-Yield Fact
A key clinical pearl to remember is that cimetidine can cause gynecomastia due to its anti-androgenic effects, a side effect not typically associated with ranitidine. This difference can significantly influence the choice of medication in certain patients.

## Correct Answer: C.