Strong metal tools allowed bronze afe farmers to grow surpluse crops and trade them with neighbors for goods such as tools . the farmers needed a method for recording their exchanges and keeping track of how much surplus they had left.

This sounds correct to me!

“the battle of stalingrad is not a turning point necessarily in strategic terms, because a lot more has to be done before the soviets can be certain of defeating germany,” says renowned world war ii historian richard overy. the germans had fought nearly a thousand miles across the soviet union to get to stalingrad.

c or d both can be the answer