The paragraph that would help build tension if added to the story is:
"As she struggled to free herself, the bus pulled into view. She waved her arms wildly, but the driver didn’t notice her. And she was still stuck. What was she going to do? She could not be late to school today."
This addition creates a sense of urgency and desperation as Sylvia is physically stuck and unable to reach the bus, enhancing the tension of the moment.