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.

He made a fake snore to pretend to be asleep.

The doctor said there is a problem with his jejunum.

Today is the day for open burning, so let's burn unnecessary papers.

I burned trash in the yard today.

I enjoyed a picnic under the clear sky.