Cloze #36 Hot 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.