A. helium
B. carbon dioxide
C. neon
D. argon

A. Zinc
B. Sulpher
C. Phosphorous
D. Acid

A. Silicon
C. Uranium
B. Germanium
D. Selenium

A. sound waves
B. Time
C. Color contrast
D. Water waves

A. Rusting of iron
B. Tempering of iron
C. Digestion of food
D. Burning of coal.

A. Reduction
B. oxidation
C. Decomposition
D. Displacement

A. Hydrogen
B. Oxygen
C. Carbon Monoxide
D. Carbon dioxide

A. Iron
B. Oxygen
C. Hydrogen
D. Nitrogen

A. Oxygen
B. Carbon di oxide
C. Nitrogen
D. Hydrogen

A. Hydrogen
B. Helium
C. Carbondioxide
D. Hydrogen sulfide