B, European settlers were immune to such diseases like smallpox because it came from their region, when knowledge that the native Americans were not immune and the disease was lethal to them, they started distributing blankets and clothing items that were infected with the viruses and caused a major impact on native population
The one of the reason's why the Allies allied themselves with the soviets was because they wanted to open a new front. The Soviet Front would be so massive and would force Axis's units to spread even more, and to spread resources more. Though they were already spread out.
