Cloze #36Hot Air Balloon

This is h_ _ air balloon. This is hot air balloon.

It is f _ _ _ _ _ with hot air. It is filled with hot air.

A burner is used to h _ _ _ the air.A burner is used to heat the air.

It makes the balloon like fl_ _ _. It makes the balloon like float.

They are f_ _ _ _ _ _up the balloon.They are filling up the balloon.

They put in c_ _ _ air first.They put in cold air first.

Why does h _ _air float? Why does hot air float?

They are f_ _ _ _ _ _up the balloon.They are filling up the balloon.

They put in c_ _ _ air first.They put in cold air first.