The correct option is C Agar-agar
A polysaccharide employed in tissue culture is agar- agar. It is a mucopolysaccharide. It is a polymer of D-galactose 3-6 anhydrous L-galactose having sulphate esterification after every ten galactose unit. It is used in the laboratory as a culture medium, stiffening and emulsifying agent. It is obtained from Gracilaria, Gelidium and Gelidielia. Thus, the correct is A.