He used a rail spike to secure the rail.

There are cats and dogs in my house.

The air in this room is fresh.

What will you use this empty box for?

Looking at the bird flying high in the sky, I felt freedom.

The altitude of this airplane is 10,000 meters.

In mathematics, an empty set refers to a set that does not contain any elements.

I enjoyed a picnic under the clear sky.

He made a fake snore to pretend to be asleep.

The doctor said there is a problem with his jejunum.