The correct option is (a) Trypsin hydrolyzing peptide linkages involving arginine or lysine
Easy explanation: Group specificity is one in which an enzyme acts on more than substrate containing particular group. Hence the example which perfectly fits the definition is trypsin hydrolyzing peptide linkages involving arginine or lysine. Lipase hydrolyzing ester bond of lipids is an example for bond specificity. Whereas, Hexokinase phosphorylating one or more kind of hexoses is an example for broad substrate specificity. L-lactate dehydrogenase will act only on L-lactic acid, and not D-lactic acid is an example for stereo specificity.