In the following items, each passage consists of six sentences. The first and the sixth sentence are given in the beginning as `S_(1) and S_(6)`. The middle four sentences in each have been removed and jumbled up. These are labelled P, Q, R and S. You are required to find out the proper sequence of the four sentences and mark accordingly on the Answer Sheet.
`S_(1)` : If we dump sewage into a stream, on a small scale, the stream dissolves it and purifies it.
`S_(6)` : For this overwhelming kind of pollution we need to coin a new term which we call super-pollution.
P : It can no longer deal even with the small quantity of sewage which it once accepted without difficulty.
Q : Ten miles downstream the water is pure again.
R: The system has broken down.
S : But if we dump large quantities of sewage, we end by killing the purifying bacteria and then the stream has lost its power to purify.
The proper sequence should be :
(a) Q-S-P-R
(b) R-S-Q-P
(c) P-R-Q-S
(d) P-Q-R-S