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.
What type of chemical can be used to remove the green layer from metal C and clean it ? Why ?