The changing of the tides and the waves that you see on the sea shore.
A. because if you have received flyers for several times for spa treatment, then you have ore options to look at and to see so you can know what the best deal is. B is wrong because billboards ( or whatever you said) are meant to want to make you impulse buy just because someone beautiful was on the front selling a product, and it won't necessarily be good or have a good deal, or be reliable.. Hope that helped! :)
