A hot -air balloon floats because hot air is lighter than cool air.
A hot-air balloon consists of a basket in which the pilot and the crew stand, a gas burner and a large balloon.To take
off, you turn on the burner which heats the air inside the balloon. When the air gets hot, the balloon rises. To land, you
allow the air inside the balloon to cool. The word which refers to
A. the air.
B. the balloon.
C. the gas.
D. the burner.
Select one of the following: