Final answer:
The sentence in question correctly uses parallel structure by maintaining the same grammatical pattern for the compared activities.
Step-by-step explanation:
The sentence "The delegates spent the day arguing with one another rather than working together to find common solutions" is indeed using correct parallel structure. Parallel structure means using the same pattern of words to show that two or more ideas have the same level of importance.
In this sentence, 'arguing with one another' and 'working together to find common solutions' are the two activities being compared. Both phrases follow the same grammatical format, which is 'verb + ing' followed by the rest of the phrase, thereby maintaining parallelism.