You are answering a USMLE-style medical question. Question: An 81-year-old man patient recently moved into an assisted living facility and presents today with itchy blisters in his axilla. He attributes these to a poor diet. He also complains that the nurse practitioner at the facility started him on 4 new medications, in addition to his existing prescriptions. On physical examination, tense axillary bullae are noted that do not rupture with light, gloved touch. On direct immunofluorescence, linear C3 and IgG deposits are seen along the basement membrane. Which of the following is the most likely diagnosis? Options: A) Staphylococcal scalded skin syndrome B) Bullous pemphigoid C) Pemphigus vulgaris D) Cicatricial pemphigoid Reply with ONLY the letter of the correct answer (A, B, C, or D). No explanation.