World War I began when Austria-Hungary declared war on Serbia in 1914. Which of the following directly caused other countries like Germany, Britain, France, and Russia to join the war? A. They needed to join a war to improve their economies. B. Their armies started fighting each other without permission. C. They had alliances with countries that were involved. D. They wanted the chance to attack and invade Serbia, too.
because their were two groups it was the triple alliance vs the triple entente so the triple alliance and germany ,austriahungry and italy was counter balanced by the triple entente of,france ,russia and great britian.it is c