When dilute HCI is added to a white substance (A), a colourless gas (B) is evolved. When the gas (B) is passed through clear lime water, a white precipitate ( C) is obtained. The precipitate dissolves when excess of the gas (B) is passed through the lime water. The residue obtained on heating the solid substance (A) is yellow when hot but white when cold. When the gas (B) is passed through red hot charcoal, another gas (D) is obtained. The gas (D) gets absorbed in arnmoniacal cuprous chloride solution . Identify (A), (B), (C) and (D) and give the relevant reactions.