When the stomach, small intestine, and large intestine work together to process food, they form a functional unit known as an organ system. Thus, the correct option is A.
What is an Organ System?
An organ system may be defined as a cluster of organs that work together to perform a specific bodily function.
Here, the stomach, small intestine, and large intestine constitute an organ system known as the digestive system.
Therefore, the correct option is A.
To learn more about the Organ system, refer to the link:
https://brainly.com/question/545314
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