You are answering a USMLE-style medical question. Question: A 66-year-old man comes to the physician because of fatigue and swelling of his legs and feet for 6 weeks. During this time he has felt like his eyes have been unusually puffy in the mornings and his urine has been frothy. He has hypertension and rheumatoid factor-positive rheumatoid arthritis. Current medications include amlodipine, methotrexate, and ibuprofen. He does not smoke. He has a history of chronic alcohol abuse. His temperature is 36.7°C (98°F), pulse is 80/min, and blood pressure is 148/86 mm Hg. Physical examination shows pallor, periorbital edema, 2+ pedal edema, and ascites. He has swan-neck deformities and nodules of multiple fingers and swelling and restricted range of motion of bilateral knee joints. Laboratory studies show: Hemoglobin 8.2 mg/dl Prothrombin time 12 seconds Serum Albumin 2.8 g/dl Total bilirubin 1.0 mg/dl Alkaline phosphatase 120 U/L AST 20 U/L ALT 19 U/L Urea 18 mg/dl Creatinine 1.2 mg/dl Urine Protein 3+ WBCs 5–10/hpf RBCs negative Bacteria negative Ultrasound of the liver and kidneys shows no abnormalities. Which of the following is the most likely cause of this patient's findings?" Options: A) Adverse effect of ibuprofen B) Decreased cardiac ejection fraction C) Renal deposition of AL amyloid D) Increased serum amyloid A production Reply with ONLY the letter of the correct answer (A, B, C, or D). No explanation.