The correct option is C Vestibulum
Paramecium is a slipper shaped protozoan. The feeding apparatus in Paramecium consists of a shallow ciliated groove, a ciliated tube which leads into the body, and a bundle of fibers (esophageal fibers) which extend from the tube nearly to the posterior end of the body. The tube is composed of an outer part (the vestibulum) and an inner part (the pharynx).