Sentence 1: Cal was heartbroken when his old dog got very sick. 
 Sentence 3: Cal cried for days and days 
 Sentence 4:  Soon, his parents surprised him with a brand new puppy 
 Sentence 5:  Cal cherished his new dog but would never forget his old dog, either 
 Given Sentence 2: The vet said the dog had to be put down.