The natives of the Carribean P : regarded the papaya Q : because of its ability R : as a magic tree S : to keep them healthy The Proper sequence should be:

• R (because of its ability) is the reason why the natives of the Caribbean regarded the papaya as a magic tree.
• P (the natives of the Caribbean) is the subject of the sentence.
• S (to keep them healthy) is the effect of the papaya’s ability.
• Q (as a magic tree) is the description of the papaya.

Therefore, the correct sequence is: RPSQ.