The Subsidiary Alliance system was extremely advantageous

• Ordering of Sentences

S1 : The Subsidiary Alliance system was extremely advantageous to the British.

S6 : They controlled the defence and the foreign relations of the protected ally.

• P : They could now maintain a large army at the cost of Indian states.
• Q : if many war occurred in the territories
• R : either of the British ally or of the Britishers
• S : This enabled them a to fight wars far away from their own territories

This proper sequence should be

1. P Q R S
2. P S Q R
3. Q R P S
4. S R P Q

Answer

The paragraph is about Subsidiary Alliance system. "They" in sentence P refers to the British. "This" in the sentence S refers to maintaining large armies. So, S follows P.

The correct option is B.