Answer:
Scout contrasts the "ladies' world" and the "world of my father" but saying at home she can do as she pleases, and she can act like a boy, but outside an at school she has to be nice and dress up. ... When Scout goes to kill a roly-poly, Jem stops her.
Explanation:
It means exactly what it says...to write about what you know. If you know about something than you'll have more to say and have an opinion. If you don't know about a subject...there's less to say.
The answer is buy as it means purchase while by is a preposition
