. . "(II) is a compound containing in a molecule at least one hydrogen atom directly attached to a silicon atom and a divalent linkage --(CR1 R2)n -- wherein each of R1 and R2 is a hydrogen atom or a substituted or unsubstituted monovalent hydrocarbon group having 1 to 10 carbon atoms and letter n is an integer of from 2 to 30." . . . . .