(A) a first organopolysiloxane compound represented by the general unit formula in which the subscripts a, b and c are each a positive number with the proviso that a:(b+c) is in the range from 0.5 to 2, R is, each independently from the others, a monovalent hydrocarbon group having 1 to 10 carbon atoms and X is a hydrogen atom or a monovalent group represented by the general formula in which R has