Considering that complementary goods have a negative cross of elasticity, it is correct to assume that the increase of the price or demand of one goods will result in an increase of price and demand of the other.
By that only, we can rule out answers A and B.
Since the products, as the name states, are complementary, there is no logic associated with the idea of consuming more of one good meaning less of the other (considering what was stated above), so it can't be the letter C.
It is D
"An increase in the demand for one will usually result in an increased demand for the other"
The Roman empire being gigantic at one point covering most of Europe, North Africa, and some of Asia was impossible to rule. The outer most towns and cities we're not really being ruled at all. so the Roman empire probably separated to make it easier to rule all of the empire at once.
B. The states had been taxing each other to pay off their debts from the Revolution and make profits to better their state. With the creation of the Constitution, the states would consolidate their debts and everyone would help pay it off. The Southern States didn't like this idea because they had little debt from the war and some had already paid it off.
This is the dynastic cycle