Answer: B. It had a strategic location along the Volga River.
When German forces attacked the western part of Russia intending to take Moscow, Joseph Stalin, then head of state of Russia led the successful defense and rebuff of the German forces. With this, Adolf Hitler lobbied the Wehrmacht to occupy the Russian city of Stalingrad.
Owing to the strategic location of Stalingrad as an industrial center in Russia and its closeness to the Volga River; an important shipping route connecting western and eastern Russia, Hitler sought to claim it. The Russians were of course ready to defend their territory at all costs. This led to the Battle of Stalingrad.