P: World War I began in 1914, after the assassination of Archduke Fran
Q: Thanks to new military technologies and the horrors of trench warfare, World War I saw unprecedented levels of carnage and destruction.
R: During the conflict, Germany, Austria-Hungary, Bulgaria and the Ottoman Empire (the Central Powers) fought against Great Britain, France , Russia, Italy, Romania, Japan and the United States (the Allied Powers).
S: By the time the war was over and the Allied Powers claimed victory, more than 16 million people – soldiers and civilians alike – were dead.
Right Answer is: C
The paragraph talks about the World War I, hence P should be the first sentence as it states about the initiation of the war. R gives another basic information about the war, i.e., its participants and the sides they were in. Thus, R should be the second sentence. S mentions the consequence of Q, thus S must be followed by Q. Thus, the sequence after rearrangement is PRQS, and option C is the correct answer.