Which factor most directly resulted in great britain entering world war l

The correct answer is: German troops invaded France through Belgium on August 4th, 1914, as part of the Schlieffen Plan.

Not only had Britain promised to defend Belgium under the Treaty of London of 1839, moreover German control of Belgium would have been seen as a serious threat to Britain.

c) troops march forward in close formation against newer, more accurate weapons

explanation:

hitler's  "rise" can be considered to have ended in march 1933, after the reichstag adopted the enabling act of 1933 in that month. president paul von hindenburg had already appointedhitler  as chancellor on 30 january 1933 after a series of parliamentary elections and associated backroom intrigues.