Hi,I think quarantine has answered all of your questions
The answer is alliteration
Repeating a sequence of words at the beginning of a phrase is called 'Anaphora' in rhetoric. It is used in speeches to give emphasis to the point being discussed. Thus, the speaker wanted to emphasize his point and encourage his listeners to do something as well.
shark is to fish as crocodile is to reptile
hope that helps
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.
