Articales made of copper and bronze slowly tarnish in air and turn green, the green colour is due to the formation of:

(A) copper oxide ()
(B) copper sulphide  (X)
(C) copper oxalate   (X)
(D) all of these  (X)

Answers: Articales made of copper and bronze slowly tarnish in air and turn green, the green colour is due to the formation of copper oxide.