Which technological innovation of World War I is most closely associated with this German notice?

a. tanks

b. airplanes

c. sub-marines

d. machine guns

Option: C. submarines

Explanation:

During World War I, German Submarines performed a fundamental role in the North Sea and the war, which changed the war scenario. Germans, advance when it came to controlling submarines. Franz Becker commanded German submarines which we know today as U-boats. The new German tactic 'unrestricted submarine warfare' caused great offence in countries, particularly America and the Royal Navy.