Answer:
an express warranty
Explanation:
An express warranty is an assurance by the merchant that a product or a service will perform as the buyer expects. It is the guarantee given to the buyer that the merchandise will perform its functions as advertised in media or product branding. Express warranty can be written or oral. Through the express warranty, a seller promises the buyer of replacement or repairs of the product should it malfunction within a specified time.
John is assuring his client that the paintings are of high quality. He is guaranteeing Rachel the art will appreciate. John's statements are comparable to a commercial advert or the branding of a product. They are offering assurances that the painting will meet Rachel's expectations.