person A: We just got a new puppy.  My older dog knew to let that one out first when I got home from work.
person B: That is very cute_comma_ the little one probably couldn't hold its bladder as long. 
person A: Definitely not.  I was surprised that he knew to let the little one go first!
person B: That was very smart of him_comma_ maybe he remembers back to his puppy days.