Final answer:
The word 'cheered' is the best choice to fit into the given sentence with a positive connotation, suggesting a supportive and joyful atmosphere at the marathon.
Step-by-step explanation:
When selecting a word with a positive connotation for the given sentence, we should look for one that implies enthusiasm and support without any aggressive undertones. Among the options provided (‘cheered,’ ‘roared,’ ‘screamed,’ ‘yelled’), the word ‘cheered’ best fits the sentence. It suggests that the marathon spectator in the unicorn onesie was providing positive encouragement and had a joyful presence at the event. Hence, the completed sentence reads: The marathon spectator in the unicorn onesie cheered at the runners as she gave them high fives when they passed her.
Other words like 'screamed,' 'yelled,' and 'roared' may suggest a more intense or aggressive action, which doesn't align with the desired positive connotation expressed through the context of giving high fives at a marathon, where the atmosphere is typically festive and supportive.