Answer:
The mucosa, or mucous membrane layer.
Explanation:
It is the innermost tunic of the wall. It lines the lumen of the digestive tract. The mucosa consists of epithelium, an underlying loose connective tissue layer called lamina propria, and a thin layer of smooth muscle called the muscularis mucosa.
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The middle one is the answer
B is your answer, it can indicate when you are working above, below, or in your target zone.
