The correct answer is B) bandwagon appeal.
More people use Sparkle toothpaste than any toothpaste made. The propaganda technique that is employed in this slogan is bandwagon appeal.
When advertisers use the bandwagon appeal, what they are trying to accomplish is applying a specific style of propaganda to get a segment of the audience to jump in and accept a marketing proposition. They want to sell the idea that "everybody is doing this, and you cannot miss it..." The focus of bandwagon appeal is to promote the desire of consumers to be part of something, to its desire to be included in something.