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 increases the urgency of Sylvia's predicament and escalates the tension of the moment, emphasizing her desperation as the bus approaches while she remains trapped.