33.Induction heating which uses electromagnetic energy is applicable to(1 Point) a. Steel b. Non-ferrous alloys c. Any electrically conducting material 34.The lightest plastic (i.e. with lowest density) is(1 Point) a. Polystyrene b. Polypropylene c. Polyethylene 35.When austenite transforms to martensite the chemical composition of the martensite is(1 Point) a. The same as that of austenite b. Differs greatly from that of austenite c. Richer carbon than austenite 36.When applied to steel, precipitation hardening is called(1 Point) a. Maraging b. Normalizing c. Full annealing 37.Annealing is carried out(1 Point) a. To reduce hardness and brittleness only b. To relieve residual stresses only c. For both a and b