A 24-year-old man presents with urethritis and dysuria; urine culture confirms Neisseria gonorrhoeae. He is prescribed ciprofloxacin 500 mg orally twice daily. Vital signs are stable (BP 118/76, HR 82, temp 37°C). At follow-up 1 week later, persistent urethral discharge and dysuria remain; urinalysis shows continued pyuria. He admits taking each dose with a large glass of milk and a calcium supplement. He denies antibiotic allergies. Which of the following best explains treatment failure?

1. A)Calcium chelates ciprofloxacin, reducing its absorption and bioavailabilityGABARITO
2. B)Calcium-resistant Neisseria gonorrhoeae emerged during treatment
3. C)Milk increases renal excretion of ciprofloxacin before absorption
4. D)Ciprofloxacin requires gastric acid for activation, neutralized by milk
5. E)Milk proteins induce hepatic metabolism of ciprofloxacin