The following sentences form a paragraph. The first and the last sentences of the paragraph are given. The rest of the sentences 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.

1. The Cossacks of Russia are a unique group of people.  

P.They are not an ethnic group,

Q.but instead, what they have a common history of being mercenary soldiers.

R. Meaning, they fought for any army that paid them. 

S.Now, they are considered a warrior tribe, 

6. and as the famous Russian writer, Pushkin, put it, are 'eternally ready to fight'.