Final answer:
Peripheral edema is a potential side effect of calcium channel blockers like verapamil.
Step-by-step explanation:
The correct answer is a) Peripheral edema. Clients taking calcium channel blockers, such as verapamil, may develop peripheral edema, which is the swelling of the extremities due to fluid accumulation. This occurs because calcium channel blockers relax and widen the blood vessels, leading to increased fluid retention in the tissues.