)which of these contributed to a long period of stalemate during world war i? the threat of atomic attacks the use of trench warfare the use of machine guns the threat of chemical weapons

The use of trench warfare contributed to a long period of stalemate during World War I.

Explanation:

Trench warfare is a form of warfare, in which the fighting armies maintain static lines of fortifications dug in the ground, called trenches. Trench warfare arose from a revolution in firearms. There were periods of trench warfare in the Civil War (1861-1865) and the Russian-Japanese War of 1904-1905, but it reached its peak of brutality and mortality on the Western Front of World War I, where this type of fighting produced a stagnation of three years, until the American forces entered the war and unleashed the conflict in favor of the allies.

b.   jim crow laws were enacted in northern states.

the answer is the government.