UPSC 2016 CDS II English Paper

'We can think of' needs an object and the most appropriate object would be 'two factors' so, 'R' will be the first sentence. 'P' will follow 'R' as it defines the object 'two factors' as confusion in the minds of the people. Now, 'QS' forms a mandatory pair after 'RP' as it is joined by a relative pronoun 'which'. So, the correct sequence will be RPQS. Therefore, option (b) is correct.