A 16-year-old patient presents with complaints of diarrhea and malaise for the past 10 days. History reveals that the patient went on a camping trip 3 weeks ago. The patient's stool specimen analysis is positive for Giardia lamblia. The nurse practitioner prescribes metronidazole (Flagyl) and informs the patient that:

Rationale: A. Giardia infections can persist or recur; monitoring is recommended even if symptoms improve. B. 7–14 days may be too soon for reliable detection of persistent infection, as cysts may not yet be shed consistently. C. A follow-up stool specimen 3 to 4 weeks after treatment ensures eradication of Giardia lamblia and confirms that the infection has resolved, especially since cyst shedding may be intermittent. D. Testing immediately upon completion of metronidazole may yield false-negative results due to intermittent cyst shedding; waiting a few weeks provides a more accurate assessment.