What Was the Main Reason Why European Diplomats Were Incapable

What was the main reason why European diplomats were incapable of slowing a rush toward war as early as late July of 1914?

A) European kings, tsars, and emperors were too bent on war to heed their advice.
B) The complex, rigid, and demanding mobilization plans devised by European army generals made immediate military action essential.
C) Ordinary people everywhere went to the polls and voted for immediate opening of the war on all fronts.
D) European industrialists, seeking to profit from mass destruction, induced the politicians they owned through bribery to push declarations of war through all European legislatures.
E) Communications was slow in a pre-computer era.