Earliest sign of putrefaction is

(D) Discoloration in right iliac fossa# The first external sign of putrefaction in a body lying in air is usually a greenish discoloration of the skin over the region of the caecum, which lies fairly superficially, and where the contents of the bowel are more fluid and full of bacteria.> Internally, putrefaction is seen on the undersurface of the liver, where that organ is in contact with the transverse colon.> The color results from the conversion of hemoglobin of blood into sulphonate haemoglobin by the hydrogen sulphide formed in large intestine and escaping into the surrounding tissues.