JEE Main 27-Aug-2021 Shift 2 Solved Paper

Barfoed's test is used to detect monosaccharides.
In this test, the aldehyde group of monosaccharides reduces Cu(II) acetate to Cu(I) oxide which result in the formation of brick red ppt.
Benedict's test is used to test the presence of reducing sugar. Copper (II) sulphate is used in Barfoed's test.
Biuret test is used to test the presence of peptide bond. The biuret reagent contains hydrated copper sulphate, sodium hydroxide and Rochelle salt (sodium-potassium tartarate). When the aqueous, solution of protein is treated with this reagent, the solution turns purple confirming the presence of amide bond. Chelated complex of Cu2+ ions formed gives purple colour to the solution.
So, correct answer is option (b) Seliwanoff's test which is used to distinguish between ketoses and aldoses. The Seliwanoff's reagent contains resorcinol and HCl.