1)
The air is indispensable to life.
2)
Wood is used in forniture manufacturing.
3)
The stars can be seen at night,and when the sun rises,the stars disappear.
4)
When the light went out,everyone lay down.
5)
The books are made of paper.
6)
Good books are sold quickly.
7)
I forgot my books at home.
8)
The book is a useful object.
9)
Silk is expensive.
