Soviet armies fighting germany benefited from
a. polish aid.
b. cold weather.
c. access to the mediterranean for supplies.
d. chinese aid.

It was due to cold weather(b).  When the Germans invaded Russia and though they brought a huge army, the whole population Russia resisted the Germans.  At first the Russians were being defeated but
Russians were able to move their plants to Siberia keeping them out the Germans reach.  When the Russian winter came, the Germans were now bogged down and the Russian launched a huge counteroffensive that that destroyed the German army retreated as the Russians recovered territories held by the Germans.  The Russian defeat would later lead to the Russian invasion of Germany at the Eastern Front.

They had to agree to slaves picking apples besides cotton.