Final answer:
The use of a celebrity to endorse a product is an example of (Option a) ethos, which refers to establishing credibility and trust in an appeal.
Step-by-step explanation:
The strategy of hiring a celebrity to endorse or support a product is an example of ethos. Ethos refers to an appeal to ethics, establishing the speaker’s or authority’s credibility and trustworthiness. Companies often use celebrities as brand ambassadors because their reputation can lend credibility to the product, convincing consumers that it is reliable by its association with someone already respected and trusted.