Cause and Effect: Which choice below represents the best option for a CAUSE of the "domino effect" of nations being dragged into the war in 1914? A. Many European countries had formed treaties and agreements with one another, pledging to come to each other's ald in the event one of the nations fell under attack in a war. With so many nations having so many of these agreements, the number of belligerents quickly increased.

B. Many of the European countries were engaged in imperialism, so once one country got involved in the fight then others stepped up their colonization in order to change their economies to suit their wartime needs.

C. As the summer of 1914 progressed after the Archduke's assassination, multiple countries felt the need to flex their military muscles and suoined the fight order to secure power and prestige for themselves

D. As the summer of 1914 progressed after the Archduke's assassination, multiple countries experienced waves of nationalism for their own political leaders, who then urged them to support military involvement in the war to showcase the pride of each nation's people​