The limbic system is responsible for controlling learning and emotional behavior
D it allows all substances to enter & exit the cell.
Adam Smith described self-interest and competition in a market economy as the "invisible hand" that guides the economy. This episode of the Economic Lowdown Podcast Series explains these concepts and their importance to our understanding of the economic system.
I'd say the answer is C Increase in plant and animal diversity.
Because grasslands are usually too dry for certain plants and animals to live there, but with more precipitation more organisms would live there.