. . . "Furthermore, the copolymerization of the monomer (A) with the monomers (B) and (C) is carried out relatively easily even in a hydrophilic solvent such as water, etc., and consequently, it is possible to improve the precipitation inhibition ability of the hydrophobic group-containing copolymer prepared markedly. [0035] The hydrophobic group-containing copolymer o" . .