How has the structure of the digestive system adapted to digest carbohydrates?
This is a fundamentally flawed question. I wonder if ‘adapted’ is a key word here, or just a careless slip on the part of the person who set the question. If you regard the word as important, then the assumption is that the digestive system in question (human?) originally evolved to handle some other primary food source. If it’s a superfluous word, then all the carb-digesting enzymes along the way (from mouth to duodenum) are there to do the job. A similar objection could be raised re the word “structure”. Structurally, you have (e.g.) salivary glands and pancreas, plus villi for absorption. You have teeth for crushing food to allow the saliva to start working, and you also have the liver storing carbs as glycogen.
