It is A, because it was only the Soviet and USA. Hope it helps!
Subsistence agriculture occurs when farmers grow food crops to feed themselves and their families. In subsistence agriculture, farm output is targeted to survival and is mostly for local requirements with little or no surplus trade.
Land needed to be cleared for farming,and since deforestation is already a problem.
Answer:
A creeping bombardment, first employed at the Battle of the Somme, featured artillery fire going forward in stages only ahead of the advancing infantry. ... The plan demanded correct timing for both the heavy artillery and the infantry to function. Failure to do that would result in their own troops being killed by artillery.
