Question

Which of these was directly responsible for the outbreak of World War I in Europe?

entangling alliances

U.S. imperialism

unrestricted submarine warfare

colonial independence movements
@Captain_Page_Turner

Answer 1

Entangling alliances, definitely.

Austria-Hungary provoked a war with Serbia, Serbia's buddies in Russia began mobilizing to protect them, and Germany jumped in with its own mobilization to protect their friends, and so on. It was a huge mess.

Answer 2

Granted, Austria-Hungary provoked Serbia after it was discovered that it was a Serbian assassin that was responsible for killing Archduke Franz Ferdinand.