You are answering a USMLE-style medical question. Question: A 2-year-old girl with recurrent urinary tract infections is brought to the physician for a follow-up examination. Renal ultrasound shows bilateral dilation of the renal pelvis. A voiding cystourethrography shows retrograde flow of contrast into the ureters during micturition. Histologic examination of a kidney biopsy specimen is most likely to show which of the following findings? Options: A) Glomerular crescents with macrophages B) Matrix expansion with mesangial proliferation C) Cortical thinning with tubular atrophy D) Thickened glomerular capillary loops Reply with ONLY the letter of the correct answer (A, B, C, or D). No explanation.