Which is the correct order of events that occurred after Austria-Hungary declared war on Serbia?

Russia mobilized its forces, prompting Germany to declare a two-front war against Russia and France.

France mobilized its forces, prompting Germany to declare a two-front war against France and Russia.

Germany mobilized its forces, prompting Russia and France to declare war against Germany and Austria-Hungary.

Austria-Hungary mobilized its forces, prompting Russia and Germany to declare war against Austria-Hungary and France.​