It's a format that only allows basic Pokemon that aren't fully evolved. All Pokemon are level 5. First, the moveset answers require EVs. Moonblast is pointless on Popplio because there's no reason why the opponent would use one of those type combinations over other ones. Second, even if they did, hydro pump or ice beam would be much stronger than moonblast. Popplio has weak physical attack, so ice beam would be much better for covering grass than acrobatics. (it also covers dragon, which is often switched into water attacks) Normal attacks aren't super effective on anything, so hyper voice is much more pointless than a move like ground type hidden power. Since it will be level 5, berry juice heals a lot more than any kind of berry.
You're supposed to know what the question is asking before answering it.