Final answer:
Avis used comparative advertising to position itself against Hertz by emphasizing its commitment to customer service, leveraging its status as the number two in the market.
Step-by-step explanation:
When Avis claimed, "We're number two, so we try harder," it was employing comparative advertising. This form of advertising works by directly comparing the advertiser's product to the products of competitors, highlighting the advantages or unique features of the advertiser's product. In this specific case, Avis used comparative advertising to position itself against the market leader, Hertz, by emphasizing its commitment to customer service, implied by the effort it claims to put into satisfying customers given its number two status in the market.