The following sentences form a paragraph.They are numbered as P, Q, R and S. These four parts are not given in their proper order. Read the sentences and choose the alternative that arranges them in correct order.

P. Now it is equally disheartening to know that our mountains too have not been spared.

Q. The authorities concerned must ensure that climbers are held responsible for waste collection

R. The Himalayan chain is a very fragile ecosystem and the source of many perennial rivers.

S. Many of us are aware of our oceans becoming receptacles for waste.