Final answer:
In the sentence 'One of the girls (was, were) late for class', the correct verb is 'was'. This is because the subject is singular 'one', which dictates the verb to be singular, 'was'.
Step-by-step explanation:
In the given sentence, 'One of the girls (was, were) late for class,' the correct verb to use is 'was'. This is because the subject of the predicate in this sentence is 'one', which is singular, and thus requires a singular verb. Despite the presence of 'girls' in the sentence, it is not the subject, but rather the object of the preposition 'of'. Consequently, the verb needs to agree with the singular noun 'one'. Therefore, the correct sentence is 'One of the girls was late for class.'
Learn more about Subject-Verb Agreement