Disaccharide A is a reducing sugar that forms one equivalent of D-galactose and one equivalent of D-glucose on hydrolysis with aqueous acid. Reaction of A with iodomethane and Ag2O yields an octamethyl derivative, which can be hydrolyzed with aqueous acid to give one equivalent of 2,3,4,6-tetra-O-methyl-D-glucopyran ose and one equivalent of 2,3,6-tri-O-methyl-D-galactopyranos e. If A contains an beta-glycoside link, what is its structure