The correct answer is We voted on the numerous antique cars.
Step-by-step explanation:
In the sentence "We voted on the numerous antique cars", the section "on the numerous antique cars" explains how the people "voted"; this means this phrase modifies or describes the action or verb, which is the function of an adverbial phrase. Moreover as may adverbial phrases this is placed after the action to show the relationship of the phrase with the verb. This does not occur in other phrases, for example, the phrase "who happen to be best friends" describes the noun of the sentence rather than the verb.