Step 1: Understanding the Task
The goal is to arrange the four given parts to form a meaningful sentence about the consequences of war.
Step 2: Finding the Logical Flow
Part P introduces the subject of the sentence: "the World Wars fought in the past".
Part Q provides the verb for this subject: "...stand testimony to the fact". This forms a strong opening pair, P-Q.
The phrase "the fact" must be explained by a clause, which typically starts with "that". Part S provides this clause: "that fighting wars brings...". So, S must follow Q. The sequence is now P-Q-S.
"Brings" is a transitive verb that needs an object. Part R, "severe human suffering", serves as the object of "brings". Therefore, R must follow S.
Step 3: Constructing the Final Sentence
The complete sentence reads: "The World Wars fought in the past stand testimony to the fact that fighting wars brings severe human suffering."
Step 4: Final Answer
The correct and logical sequence is PQSR. Therefore, option (A) is the correct answer.