The weapon that helped continue the stalemate on battlefields during World War I is option<em> D. Machine Gun</em>. A stalemate is a situation in which neither side has a clear victory over the other. The war becomes very long and slow, and armies have to be creative to surprise the enemy. There were many stalemates in WWI, especially in the Western Front.
It's technically false that the fall of the Berlin Wall symbolized the end of communism since communism still exists, but it did mark the end of communism in Germany.
