Answer:
The advantages of mixture a grasses and legumes is;
* extend the growing season of a pasture
* improve the quality of forage
* improve flexibility to survive environmental conditions
* reduce susceptibility to insects and disease attacks
* improve the palatability
* increase the organic matter content of the soil over time because of grass root system
* reduce weed encroachment
* reduce erosion
* produce higher yields
The probable pasture production for perennial ryegrass in the northern hemisphere leaves some time when the grass is dormant. There are times when other feed will be needed. Utilizing another grass or legume that flourishes during the less productive periods for perennial ryegrass extends the season for production and maintains the quality of feed.
Answer: Rainy and dry seasons
We can reject answers C) and D) :those are two famous cities in Russia, and cities would be too small to take up three-forths of Russia, the biggest country in the world.
Murmansk is also a city: in the North-West of Russia, in the Arctic Circle.
So the correct answer is: Siberia
B; As far as the relation between humans and the environment, it is obvious how much they relied on it. Not only as a food source, but for economic growth and sustainability as well. The other answers make valid points but in the context of this question, the only one that even mentions the relation is B.