Answer:
the high demand for factory workers
Explanation:
Chlorine and Mustard gas are types of poison gas, sometimes used during chemical warfare. For example Germany introduced their usage against the Allies during WW1.
On December 8, 1941, one day after the attack on Pearl Harbor, the United States declared war on Japan. This prompted Germany to declare war on the United States, which, in turn, led to the United States to declare war on Germany on December 11, 1941.