Sentence 1: A boy hear a siren outside the house. 
 Sentence 3: In the distance a fire truck drove towards him 
 Sentence 4:  He waved at the firemen as they passed 
 Sentence 5:  One of the firemen waved back at the boy 
 Option 1: He ran outside to see what it was. 
 Option 2: He sits and wonders if it was real.