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 labeled as P, Q, R, and S. You are required to find the proper sequence of the four sentences and mark your response accordingly.

S1: The chronology of the World War 1 is as follows
P: June 28, 1914, Archduke Francis Ferdinand is assassinated.
Q: On the 2nd of August, Germany invades Luxembourg and Belgium.
R: Austria-Hungary invades Russia on the 10th of August 
S: Austria-Hungary declares war on Serbia on July 28, 1914, beginning World War I.
S6: And the war started spreading across Europe