Sentence 1: Jackson had always had back pain after working. 
 Sentence 3: Finally a coworker recommended he buy a new pair of shoes 
 Sentence 4:  Jackson bought new shoes that were very comfortable 
 Sentence 5:  Finally his back pain was gone 
 Option 1: His job required him to stand for a long time. 
 Option 2: His boss recommended new shoes to him.