Lyddie doesn't sign the petition, because she is afraid of the consequences of that action. By signing the petition, she would publicly be associating with it and those workers. She runs the risk of being fired from her current job and blacklisted from the other mills. Lyddie cannot let that happen. She desperately needs the paycheck in order to pay back the debt that her family owes.
Answer:
It forces the boys to let go of some of society's conventions.
Explanation:
When you go through the starting few chapters, you understand that the boys are on a "deserted" island, and they immediately realize that they are pretty much stranded, without a lot of resources and adult supervision.
So they (and you, the Reader) understand that they have to just let go of some of society's convention, and adapt more to that wilderness state of mind.
i think D is the correct answer. hope it helps