The correct match among the following in ‘lac operon’.

The lac operon consists of one regulatory gene. The i gene codes for the repressor of the lac operon. The z gene codes for beta-galactosidase (b-gal), which is primarily responsible for the hydrolysis of the disaccharide, lactose into its monomeric units, galactose and glucose. The y gene codes for permease, which increases permeability of the cell to $\mathrm{\beta }$ -galactosides. The a gene encodes a transacetylase. Hence, all the three gene products in lac operon are required for metabolism of lactose.