‘P’ will be the first part of the given sequence as ‘the school masters and professors’ forms the subject. ‘Q’ will come next because it states the belief maintained by the school masters and professors, that is, ‘innate intelligence is a quality’. ‘S’ will come next as the pronoun ‘which’ refers to the ‘innate intelligence’ mentioned in ‘Q’. ‘R’ will be the last part of the given sequence as ‘but’ shows the contrast in the context of the intelligence of one individual to other. Hence, PQSR is the correct sequence. Thus, option (c) is correct.