Sentence 1: Anna was walking her dog on a sunny day. 
 Sentence 3: Anna's dog seemed very attracted to the ball 
 Sentence 4:  Anna decided to go to the pet store and buy a yellow ball for her dog 
 Sentence 5:  Anna played fetch with her dog and it became their favorite game 
 Option 1: They passed by another dog who relieving himself on a fire hydrant. 
 Option 2: They passed by another dog who was playing fetch with it's owner.