"Their" is correct, because it shows possession of the desk by someone else.
I read this book last year so take this with a grain of salt.
Gene jumps from the tree to compete with Finny due to the fact that Gene is always trying to do better than Finny. He is put under the grasp of peer pressure due to Finny almost forcing him to do this. Ever since he first jumped Finny kept pressuring him to jump since he thought Gene enjoyed jumping.
Rather than uses this answer you should probably just reread chapters 3-4
The correct answer should be
<span>to lend credibility and additional support to their conclusion
Quoting famous books is usually done to support what you're saying, it's not about proving things or demonstrating it, it's rather to help make your hypothesis seem more legitimate. Highlighting your knowledge is not necessary and sounds a bit arrogant. </span>
