Sentence 1: Julian rode his rusty bike down the street. 
 Sentence 3: He walked the bike home to his dad 
 Sentence 4:  His dad decided that Julian needed a new bike 
 Sentence 5:  They went to the store, and Julian chose a new mountain bike 
 Option 1: As he was riding he fell off the bike. 
 Option 2: As he was riding, his chain fell off and he couldn't ride anymore.