The correct answer for the question that is being presented above is this one: "oxygen became available from cyanobacteria." About 1.2 billion years ago, eukaryotic and multicelled organisms evolved because oxygen became available from cyanobacteria.
I'm sorry nobody has told you about it yet. They should. You're scared of something just because you don't know what's in there or what it looks like. Summer school is a chance to improve your grades, because it's a class where they teach the same subjects again, so you can review it and learn it a little better than you did the first time. The only difference is that they go a little faster, because the summer is shorter than the regular school year. And that's the whole story. There's nothing to be afraid of. When I went to Summer school a few years ago, I loved it. I started to understand stuff that I didn't understand very well the first time, and I really improved my grade. Good luck.
To push the enslaved to produce more crops. to render the enslaved powerless as to not revolt. to provoke fear in the enslaved to repay their cost. to harden the enslaved and ready them for auction.
Gravity is the force that acts as water moves through
