Answer:
B) Extremely cold climate conditions made it difficult to live in the region
Explanation: In places where there are countless mountain ranges, there is bound to be isolation to the point where the people that already reside there would develop their own language, culture, and mannerisms. Northern Europe is filled with mountains and cold climate. Many people from other regions in Europe would have a hard time adjusting to the harsh conditions like the natives.
Omaha and Sacramento is the answer
Grain farming is done for economic activity and this makes it commercial. It is highly specialized and mechanised. The yield per acre is low so the farms are big. The yield is high per man so little manpower is needed for production. Grain farming is subject to market conditions like climate.