What were the effects of austria’s annexation of bosnia and herzegovina?

World War I--in the end WWI is connected to the annexation as the Serbian attack on Archduke Franz Ferdinand was a response to the annexation. 

Following the Austrian annexation of Bosnia and Herzegovina, Serbian nationalists called the Black Hand planned an attack on the Archduke Franz Ferdinand's visit to Bosnia. This assassination, triggered the events which led directly to the outbreak of World War I.  

4.a depression is the answer

Slower