Final answer:
A bandwagon ad is a technique where an advertisement shows many consumers using a product, suggesting that others should also use the product to join the majority.
Step-by-step explanation:
The technique of advertising that shows multiple consumers using a product to build consumer trust is known as a bandwagon ad. This method capitalizes on the bandwagon effect, where the prevalence of product usage among a large number of people is meant to convince others that the product is worth purchasing. The implication is that a consumer should join the crowd to avoid being left out or because the product is perceived as popular and therefore reliable or superior.