Final answer:
The word 'ever' in the sentence 'Have you ever been to Hunza Valley?' serves as an adverb. It is used to modify 'been' and indicates any time frame in the past.
Step-by-step explanation:
In the question "Have you ever been to Hunza Valley?", the word 'ever' is known as an Adverb in grammar. Adverbs are used to modify verbs, adjectives, or other adverbs, often used to indicate time, manner, place, or degree.
In this particular sentence, 'ever' is used as an adverb of time to question if at any time in the past, you have been to the Hunza Valley.
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