P : it becomes difficult
Q : satisfying our desire
R : but once we set about
S : if not impossible to restrain them

The Proper sequence should be:

A. PQRS

B. QRPS

C. RQPS

D. RQSP

Answer: Option C

Solution(By Examveda Team)

But once we set about satisfying our desire it becomes difficult if not impossible to restrain them.