Answer: Hot air is less dense than cool air; the heated air causes the balloon to rise simply because it is lighter than an equal volume of cold air. Buoyancy is an upward force that the air exerts, and it helps hot-air balloons and blimps stay in the air. A hot air balloon uses a burner to heat up the air inside the balloon.
Glasnost (openness) and Perestroika were the policies adopted by Mikhail
Gorbachev (answer C.) to save the Soviet economy- Gorbachev received Nobel Peace Prize for this.
The fire was started by a Dutch communist named Marinus van der Lubbe.
Personal feelings about a political matter.
