When an object made of metal A is kept in air for a considerable time, it loses its shine and becomes almost black due to the formation of a layer of substance B. When an object made of another metal C is kept in damp air for a considerable time, it gets covered with a green layer of substance D. Metal A is the best conductor of electricity whereas metal C is the next best conductor of electricity.
(a) What is metal A?
(b) What is metal C?
(c) Name the substance B.
(d) Name the substance D.
(e) What type of chemical can be used to remove the green layer from metal C and clean it? Why?