Answer:
physical system, human systems, environment, society, geography, and regions
I believe the answer is Model.
A model is created after we've done analyzing all related concepts and make an effort to structure it in something that can be implemented.
for example, Before Real Estates company develop build an apartment, they will always make a smaller model as some sort of guidance that become a basis to build the actual building.
Answer: one person
Explanation: The opening phrase is sung by one person before other voices enter and sing together.
Fairy Tail is a guild. Weeb jokes aside, apprectices helped because they also became trade workers. Guild is essentially the same thing, just where groups of people join together, and they all do the same thing.