Answer:
the main cause or main effect.
Explanation:
Whenever writing an essay, you should always bring it back to your main point or claim. If your focus is on a cause-and-effect, then you should always tie your details back to that.
This is part of Tom's plan to entice the other boys into painting the fence for him. He plays on their emotions in order to convince them that painting the fence is a "fun" thing to do.
I believe an example of a periodical is the "People Magazine".
Not sure but i read other sources and they said its true. But I can't say its going to be right.