Final answer:
The three adverbs in the sentence 'One line of customers stood outside waiting to purchase the video game at the stroke of midnight' are 'outside', 'waiting', and 'at'.
Step-by-step explanation:
The question asks to select the three adverbs from the sentence provided: One line of customers stood outside waiting to purchase the video game at the stroke of midnight.
The adverbs in this sentence are: outside, waiting, and at.
Adverbs are words that modify verbs, adjectives, or other adverbs by providing additional information about how, when, where, how much or in what manner something happens. In the provided sentence, 'outside' describes where the customers stood, 'waiting' describes how they stood, and 'at' indicates the specific time they were standing.