**Core Concept**
Bradykinin is a peptide that causes vasodilation and increased vascular permeability, leading to hypotension and edema. Its effects are mediated through the bradykinin receptor, which activates the Gq protein-coupled signaling pathway.

**Why the Correct Answer is Right**
Drugs that inhibit the enzyme angiotensin-converting enzyme (ACE) will enhance the effects of bradykinin. ACE is responsible for breaking down bradykinin into its inactive metabolites, and by inhibiting this enzyme, bradykinin levels increase, leading to enhanced vasodilation and increased vascular permeability. This is the mechanism behind the use of ACE inhibitors in the treatment of hypertension and heart failure.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because beta-blockers, such as propranolol, actually reduce the effects of bradykinin by blocking the beta-2 receptors, which are involved in vasodilation.
**Option B:** This option is incorrect because calcium channel blockers, such as nifedipine, also reduce the effects of bradykinin by blocking the influx of calcium ions into smooth muscle cells, thereby reducing vasodilation.
**Option C:** This option is incorrect because alpha-blockers, such as phentolamine, actually increase the effects of bradykinin by blocking the alpha-1 receptors, which are involved in vasoconstriction.

**Clinical Pearl / High-Yield Fact**
ACE inhibitors can cause a dry cough in some patients due to the accumulation of bradykinin and its metabolites, which stimulate the cough center in the brain.

**Correct Answer: D. ACE inhibitors.