(b) Stomach and anus
The exit of food from the stomach is regulated by a sphincter muscle, and the exit of waste material from the body is regulated by the anal sphincter.
The passage explicitly mentions two sphincter muscles: one at the exit of the stomach (regulating food entering the small intestine) and the anal sphincter (regulating removal of waste via the anus). No sphincter is mentioned at the oesophagus, small intestine, or large intestine junction in this context. Always look for exact terminology in the source text for MCQs.
Source: Life Processes, Section 5.2.4