10 ml of freshly prepared iron sulphate solution was taken in each of four test tubes. Strips of copper, iron, zink and aluminium were introduced, each metal in a different test tube. A black residue was obtained in two of them. The right pair of metals forming the precipitates is:

(a) zinc and aluminium (b) iron and aluminium (c) copper and zinc (d) aluminium and copper

Class XIII.