Rhetoric is the art of persuasive speaking or writing.
By explaining problems and giving solutions! this is the best fit because the other two might make sense at a first glance, but only explaining problems and solutions would be an effective way to teach people how to set up an aquarium by giving them examples of what to do and what not to do whereas the others are just him talking about his aquarium.
Use the evolution of the very first phone then just elaborate on the progression of apps and miscellaneous things we have on our phone