Because it does not say dear (put inserted name here) and then start the email/letter
Answer:
#8. The twins took their dogs, Muttsy and Flopsy, for a walk in the park.
Explanation:
#9. Jeff wants to be just like the Cookie Monster!
#10. Some people don't like Barney.
#11. Logan is Wolverine's real name, but he is also called Patch.
Answer:
so, the first sentence informs you that it's raining cats and dogs. when you add the comma after raining, the meaning completely changes. the speaker is telling the cats and dogs that it is raining.