A nurse is reinforcing teaching with a client who has primary open-angle glaucoma and a new prescription for timolol eye drops. Which of the following statements indicates an understanding of the teaching?

A. "This medication will dilate my eyes": Timolol is a beta-blocker used to reduce intraocular pressure in glaucoma. It does not cause pupil dilation; in fact, it does not affect pupil size significantly. Believing it dilates the eyes reflects a misunderstanding of its action. B. "This medication will darken the color of my eyes": Timolol does not change eye color. Eye color changes are associated with prostaglandin analogs like latanoprost, not beta-blockers. This statement indicates incorrect knowledge about the medication. C. "I should check my heart rate while taking this medication": Timolol can be absorbed systemically and may decrease heart rate or cause cardiac side effects. Monitoring pulse rate ensures early detection of bradycardia or other cardiovascular effects, demonstrating correct understanding of safety precautions. D. "I should take a zinc supplement while taking this medication": There is no indication that timolol requires zinc supplementation. Taking unnecessary supplements does not enhance drug efficacy and may introduce additional risks or interactions.