You are answering a USMLE-style medical question. Question: A 24-year-old woman gravida 2, para 1 at 24 weeks' gestation comes to the physician for a prenatal visit. She feels well. Her earlier pregnancy was uncomplicated. This is her 4th prenatal visit. She had an ultrasound scan 2 weeks ago that showed a live intrauterine pregnancy consistent with a 22-week gestation with no anomalies. She had a normal Pap smear 2 years ago. Vital signs are within normal limits. Pelvic examination shows a uterus consistent in size with a 24-week gestation. Her blood group and type is B positive. Which of the following is the most appropriate next step in management? Options: A) Oral glucose challenge test B) Cardiotocography C) Swab for GBS culture D) Tdap vaccination Reply with ONLY the letter of the correct answer (A, B, C, or D). No explanation.