How was the united kingdoms's role in the events leading to world war i different from that of germany

The United Kingdom was tied by alliance to France and Belgium (as well as to Russia).  Germany was tied by alliance to Austria-Hungary (and also to Italy, but Italy would later change sides).   Those alliances would kick in as World War I erupted -- in particular, Germany's alliance with Austria-Hungary would have a key role in starting the war.

The United Kingdom had the world's strongest navy in the years building up to World War I, and Germany was doing all it could to build up its naval capabilities to catch up to the British.  The competition for supremacy was a big part of the events leading up to World War I.

When the Austrian prince Franz Ferdinand was assassinated, the German alliance kicked in before the British were directly involved in any way.  Russia had mobilized its armies against Austria, to come to the defense of Serbia as an ally.  (The assassination of Franz Ferdinand was carried out in Serbia by a Serbian nationalist group.)  Germany warned Russia to halt its troop mobilization, and when the Russians did not do so, Germany went to war. However, the German war plan, based on Russia's alliance with France, was to go and attack France first.  The Germans went through Belgium in their attack on France.  Both as a guarantor of Belgian neutrality and as an ally of France, thus the United Kingdom became involved in the war.

So, both Germany and the United Kingdom were reacting to events, but they also were both causes of the events that were leading to the war.  Increasing militarization and alliance systems were a big part of the events leading to World War I, and both Germany and the UK were involved in that.

The correct answer is b