The sky is very beautiful, isn't it?

Seeing the empty cup, he poured another cup of tea.

There is not a single cloud in the sky.

Altostratus clouds are spreading in the sky, it looks like it's going to rain.

He lied to conceal the truth.

The altitude of this airplane is 10,000 meters.

He made a fake snore to pretend to be asleep.

I enjoyed a picnic under the clear sky.

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

He wants to make a car that can fly in the air.