Answer:
D. submucosa
Step-by-step explanation:
The submucosa is a thick layer of loose connective tissue that lies beneath the mucosa. It contains glands, blood vessels, lymphatic vessels, and a nerve plexus called the Meissner's plexus. The Meissner's plexus helps to regulate digestive activity by controlling the secretion of digestive juices and the movement of food through the digestive tract.
The other layers of the alimentary canal do not contain all three of these components.
* The mucosa is the innermost layer of the alimentary canal and is made up of epithelial cells and a thin layer of connective tissue. It contains glands that secrete digestive juices and mucus.
* The serosa is the outermost layer of the alimentary canal and is made up of a thin layer of connective tissue that is covered by a layer of simple squamous epithelial cells. It helps to protect the alimentary canal from the surrounding environment.
* The muscularis externa is the middle layer of the alimentary canal and is made up of smooth muscle. It helps to propel food through the digestive tract.
Therefore, the submucosa is the layer of the alimentary canal that contains not only glands and blood vessels, but also a nerve plexus that helps regulate digestive activity.