Answer:
16. The bird's egg is blue.
17. I like the smell of roses.
18. Diamonds are a girl's best friend.
19. David's mom is very tall
20. My brothers are twins.
Step-by-step explanation:
A singular noun names one person, place, thing, or idea, while a plural noun names more than one person, place, thing, or idea. Most singular nouns need an 's' at the end to become plural. Adding an 's, to the end of a singular noun, can mark it as plural, or mark a possession of something. We see this instance, in sentence 19.