What did austria-hungary do in 1908 that increased pre-war tensions in europe?
it annexed bosnia and herzegovina.
it annexed serbia and herzegovina.
it attacked serbia and herzegovina.
it attacked bosnia and herzegovina.

It annexed Bosnia and Herzegovina.

Explanation:

The Bosnia and Herzegovina provinces were under the authority of Ottoman Empire until it was annexed by Austria-Hungry On October 6, 1908. The annexation of the these provinces by the Dual Monarchy of Austria-Hungry disrupted the balance of power all over Europe.The annexation angered Serbia and the Balkans. Furthermore, Austria's invasion of Serbia prompted Russia to intermediate in the conflict. With Germany supporting Austria-Hungary, the tension among these countries got more worse which eventually led to the First World War.