Which is the most appropriate claim to include in a sponsored ad running in May 2022?

The most appropriate claim is "Leave teeth three shades whiter than other brands. Research completed by Dental Weekly Magazine, April 2022" because it provides a specific, verifiable claim with recent supporting evidence. Ad claims, especially those making comparative statements, require substantiation. The research date of April 2022 is current and relevant for an ad running in May 2022, making the claim credible. The other options are less appropriate: "Leave teeth three shades whiter than other brands" lacks substantiation, which is often required for such claims. "Leave teeth three shades whiter than other brands according to experts" is vague; it doesn't specify which experts or when they made this assessment. "Leave teeth three shades whiter than other brands. Research completed by Dental Weekly Magazine, April 21, 2019" uses outdated research. Claims should ideally be supported by recent data to remain relevant and accurate.