Prior to the beginning of world war i which nation challenge great britain before supremacy of the seas

Immediately prior to World War I, the only nation that challenged British naval supremacy was the Imperial German Navy. Since the British had entered amicable treaties with other European (France, Russia) and Asian powers (Japan) only the German Imperial navy remained as an opponent to the British naval supremacy.

Between 1900 and 1914 the nation which considered Great Britain a threat was Germany under the rule of Kaiser Willhelm II and his eagerness to build a naval fleet capable of challenging Britain´s.

From 1898 on, Germany began to build a battle fleet, which encouraged Great britain to join the naval race, focusing on the construction of a new class of battleship: The Dreadnought, which would be the lead for new battleships thereafter.

Great Britain was by far the most powerful naval force in the world at the time, Germany was aware of this. Germans did not expect to defeat Great Britain but to force them to make diplomatic concessions, however, any threat to Great Britain´s Naval power was considered a threat to the nation itself, since one of Britain´s main strengths was sea trade.

Altough this arm race had been going for years now, it was not until    Germany´s Bill 0f 1908 that the damage to the Germany-Britain relationship proved to be irreversible and Britain was forced to meet the German challenge; Being this was of the causes of the conflict in 1914.

the answer to your question is:

strong-mayor system