A 16-year-old adolescent female reports amenorrhea for 8 weeks. The most appropriate intervention by the nurse practitioner would be to:

Rationale: A. Asking about sexual activity is important for history-taking but does not directly confirm or rule out pregnancy. B. Ordering a urine pregnancy test is the most appropriate first step in evaluating secondary amenorrhea in a sexually active adolescent, as pregnancy is the most common cause. C. A serum HCG test is more sensitive than a urine test and may be ordered if the urine test is inconclusive, but initial evaluation typically starts with the less invasive urine test. D. Pelvic ultrasound is not the first-line evaluation for amenorrhea and is reserved for cases where structural abnormalities are suspected or pregnancy is confirmed and further assessment is needed.