Final answer:
The correct way to hyphenate the underlined part of the sentence is 'an average 2,000-calorie diet'.
Step-by-step explanation:
The correct way to hyphenate the underlined part of the sentence is an average 2,000-calorie diet. The hyphens are used to connect the words '2,000' and 'calorie' with 'diet' to create a compound adjective. It is important to note that the hyphens are not needed between 'average' and '2,000' because 'average' is an adjective modifying '2,000-calorie diet' as a whole.
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