Question

the
intense heat of summer
intense cold of winter
lack of access to water
mountainous terrain made fighting on russian soil especially difficult for german troops.

Explanation:

In the context of German troops' fighting on Russian soil (especially during World War II), the intense cold of winter was a major challenge. The harsh winter conditions, including extreme cold, disrupted German supply lines, equipment functionality, and troop morale, making warfare extremely difficult. The other options: intense summer heat was not as defining a challenge as winter cold; Russia has sufficient water sources, so lack of water is incorrect; and Russian terrain is not predominantly mountainous in the key war zones (like the Eastern Front) compared to the impact of winter.

Answer:

B. intense cold of winter