(a) 2 molecules of glucose. (b) Intramolecular hydrogen bonding. (c) Vitamin $B_{12}$. OR (a) Hydrolysis of sucrose brings a change of sign of rotation from dextro(+) to laevo(-) and the product is named as invert sugar. (b) Protein found in biological system with unique three dimensional structure and biological activity is called native protein. (c) A unit formed by the combination of nitrogenous base, pentose sugar and phosphate.