47. 腸道黏膜層的M細胞(microfold cells)是一種什麼細胞? (A)抗原呈現細胞(antigen-presenting cells) (B)內分泌細胞(endocrine cells) (C)黏液分泌細胞(mucus-secreting cells) (D)吸收性細胞(absorptive cells)