‘Q’ will be the first part of the given sequence as it describes the state of the boys mentioned in the given statement, that is, ‘invariably dependent’. ‘P’ will come next as it tells us about the thing that boys are dependent on, that is, ‘on their parents’. ‘R’ will come next as it starts with the word, ‘until’ which means ‘up to the point in time or the event mentioned’. ‘S’ will form a logical phrase with ‘R’ as it completes the condition mentioned in ‘R’. Hence, QPRS becomes the right sequence of words. Hence, option (d) is correct.