Answer and Explanation:
Well if I listened well in Chemistry class,
a. Carbon dioxide is used as fire extinguisher because carbon dioxide can displace oxygen ( which is one of the major three elemnts that make up fire or also known as the fire triangle ).
Also, carbon dioxide is cold so it can cool down the fuel.
b.Liquid Nitrogen is used in freezing food due to it's cooling properties which creates little crystals around the solid food particles without affecting the taste of the food.
c. The argon prevent filaments from decaying. In incandescent light bulbs , the tungsten filaments produces heat which produces light