You are answering a USMLE-style medical question. Question: A 53-year-old man comes to the physician because of a 2-month history of multiple episodes of small amounts of blood in his stools. Examination shows pale conjunctivae. His hemoglobin concentration is 8.3 g/dL and mean corpuscular volume is 72μm3. Colonoscopy shows a 2.3-cm polypoid mass in the ascending colon. A photomicrograph of a biopsy specimen of the lesion is shown. Which of the following processes is most likely to be involved in the pathogenesis of this patient's condition? Options: A) Underexpression of COX-2 B) Increased phosphorylation of serine and threonine C) Impaired degradation of β-catenin D) Abnormal transfer of phosphate to cellular proteins Reply with ONLY the letter of the correct answer (A, B, C, or D). No explanation.