Why Was Great Britain's Role Important in the Beginning of World

Why was Great Britain's role important in the beginning of World War I?

A) Britain had refused to join any alliances before World War I.
B) Britain's intentions were unclear,which made some leaders think it might join Germany's alliance.
C) Britain clearly signaled its intention to enter the war if Germany attacked France.
D) Britain clearly signaled its intention to enter the war if Germany attacked Poland.
E) Britain's intentions were unclear,which made German leaders doubt whether Britain would enter the war.