Answer:
D. muscularis externa
Explanation:
The gastrointestinal tract or digestive tract consist of four main layers:
• Mucosa- consists of the epithelium together with glandular tissue and the lamina propria (connective tissue)
• Submuscosa- consists of fibrous connective tissue with larger blood vessels, lymphatics, nerves..
• Muscularis externa-smooth muscle layer that consists of three layers, responsible for movement (propulsion) and physical break down of the food
• Serosa-consists of connective tissue continuous with the peritoneum.
