Why does Duane Jr need to borrow Nick's biology book?

Duane Jr. needs to borrow Nick's biology book because his backpack is gone, which indicates that he does not have access to his own materials required for studying. Since he needs to prepare for an exam, borrowing Nick's book allows him to access the necessary information to study effectively. The urgency to study for the exam makes this choice the most logical, as without the textbook, he would be at a disadvantage in preparing adequately for the upcoming test.