Before World War I, France and Russia had a military alliance. This meant that each country promised to support the other in the event of war. In 1914, Germany declared war on Russia. By the end of the year, both French and Russian troops were battling the German military. Which of the following, if true, would suggest that the military alliance was the cause of France entering the war with Germany?

A.France declared war on Germany immediately after Germany declared war on Russia. B.Russia and France's military alliance was signed by leaders who are no longer in power. C.Russia and France both had extremely powerful militaries during the war. D.French leaders had been planning a sneak attack against Germany since 1913.