Sentence 1: Gina had a sweet dog. 
 Sentence 3: Gina was sad, knowing that she would have to put him to sleep soon 
 Sentence 4:  As he got older and older, his health failed 
 Sentence 5:  Gina knew it was time to take him to the vet 
 Option 1: It was getting to be very old. 
 Option 2: It was a very young puppy that she got a few months ago.