I am going to say B because it seems most appropriate.
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.
Answer:
hiya daden-san my acc is normal now im back on this one gotta get all me fookin points back 0-0 imma add something funny =-=
Explanation: