Which of the following was directly caused by austria-hungary declaring war on serbia? (5 points)
select one:
a. russia mobilized its troops.
b. germany declared war on russia and france.
c. britain declared war on germany.
d. germany attacked luxembourg.

The direct consequence of Austria-Hungary declaring war on Serbia was that Russia mobilized its troups as it was in good relations with Serbia at the time (and still is today). It did this as it knew what was about to happen and that large-scale war was basically inevitable.