Ex 1.
table -> tables
lamp -> lamps
bag -> bags
goose -> geese
couch -> couches
knife -> knives
family -> families
house -> houses
eraser -> erasers
fly -> flies
stereo -> stereos
class -> classes
play -> plays
armchair -> armchairs
window -> windows
person -> people
tooth -> teeth
shelf -> shelves
Ex 2.
1. This is an armchair. -> These are armchairs.
2. I am a student. -> We are students.
3. It is a couch. -> They are couches.
4. There is a lake near the house. -> There are lakes near the houses.
5. What is this? It’s a stereo. -> What are these? They are stereos.
6. What is that? It’s a bookshelf. -> What are those? They are bookshelves.
7. That is an eraser. -> Those are erasers.
8. It is a ruler. -> They are rulers.
Ex 3.
1 - A. a
2 - A. it's
3 - C. but
4 - C. next to
5 - D. in front of
6 - C. goes
7 - C. there are
8 - D. with 
9 - A. me
10 - C. many