How did the development of trench warfare influence the course of World War I?
A. It helped the war spread across Europe by allowing troops to be
more mobile.
B. It increased the death toll from the war by encouraging soldiers to
target civilians.
C. It extended the war by preventing either side from capturing much
territory
D. It brought the war to an end by introducing new technologies to
break the stalemate.

Trench warfare is a type of land warfare using occupied fighting lines largely comprising military trenches, in which troops are well-protected from the enemy's small arms fire and are substantially sheltered from artillery. Trench warfare became archetypically associated with World War I (1914–1918), when the Race to the Sea rapidly expanded trench use on the Western Front starting in September 1914.

Explanation:

No state had an intention for a long war. They were all hoping for quick victory. However the development of trench warfare made WW1 the war of attrition. Trench warfare had a massive impact on soldiers as it caused huge amounts of casualties on the battlefield and also caused health problems of the battlefield. Much of the war along the western front was fought using trench warfare. Both sides dug long lines of trenches that helped to protect the soldiers from gunfire and artillery. The area between enemy trenches was called No Man's Land. Trench warfare caused a stalemate between the two sides for many years.

it increased the power of the king of england.