The answer is A, natural selection.
Federalism is a mixed or compound mode of government that combines a general government with regional governments in a single political system. Its distinctive feature, first embodied in the Constitution of the United States of 1789, is a relationship of parity between the two levels of government established.
Answer:
If you the unit prices you know the cost per unit. For example, you would be able to compare possibly a price per one ounce of Dasani water and a price per one ounce of Aquafina water. This makes it super simple to compare the prices of the two brands when they are both written as a unit rate (of course, the units would need to be the same to make the comparison).
Explanation:
