The paragraph that would help build tension if added to the story is:
"She yanked hard on the backpack and heard a tearing sound, but she didn’t care. The bus was coming to a stop. She raced to it, climbed on, and slumped down into her seat, relieved. That was too close for comfort, she thought to herself."
This addition heightens the urgency of Sylvia's situation and emphasizes her anxiety about potentially missing the bus, making the reader feel the tension of the moment.