A clinician explains to medical students why urinary tract infections are less common in individuals with normal urinary physiology. Which group of factors best represents the body's natural defenses against bacterial colonization in the urinary tract?

Weak urethral sphincters, high urinary glucose, infrequent bladder emptying

Sterile bladder environment, no urinary microbiota, absence of organic molecules

Continuous urine flushing during voiding, urethral sphincter barriers, antimicrobial substances in urine

Bacterial generation by bladder epithelial cells, reduced urine flow, stable neutral pH