‘R’ will be the first part of the given sequence as the possessive pronoun ‘his’ is used in the context of ‘Chandran’ in S1. ‘S’ will follow next as the pronoun ‘it’ is used in relation to ‘pen’ in ‘R’. ‘Q’ will follow next as it tells what happens when he thought that he has lost his pen, that is, ‘just then his sister enters’. ‘P’ will come next as it tells that the pen was found in her sister’s hand. Hence, RSQP is the correct sequence. Thus, option (b) is correct.