A 25-year-old female presents to the ED with a complaint of lower abdominal pain, vaginal bleeding, and fever. She underwent an induced abortion 2 weeks prior to presentation. Which of the following tests is MosT helpful in the management of this patient?
(A) Pelvic ultrasound.
(B) Complete blood count.
(C) Urinalysis.
(D) Urine $\beta$-hCG.