The correct option is D Secretin
Thyroxine was the first thyroid hormone to be isolated and crystallized in 1914. Testosterone was first isolated in 1935. Epinephrine was the first hormone to be isolated in crystalline form in 1931. Bayliss and Starling, 1902, discovered presence of secretin in acidic extracts of duodenum which was then isolated and sequenced by Jorpes and Mutt. This makes option D correct.