In this section, each item consists of six sentences of a passage. The first and sixth sentences are given as SI and S6. The middle four sentences in each have been jumbled up and labelled as P, Q, R and S. You are required to find the proper sequence of the four sentences and mark your response accordingly.

S1: We have seen that all metals are not equally reactive.  
P:  But all metals do not react with these reagents. 
Q: We checked the reactivity of various metals with oxygen, water and acids.  
R: So we were not able to put all the metal samples we had collected in decreasing order of their reactivity. 
S: Displacement reactions give better evidence about the reactivity of metals.
S6: It is simple and easy if metal A displaces metal B from its solution, it is more reactive than B.