The rise in the cost of fertilizer represents a change in input prices, which is a determinant of supply, not demand. All other options represent determinants for demand.

If demand for widgets increases when incomes decrease, then the income elasticity for widgets is negative. This is because income elasticity is E = percent change in quantity/percent change in income. If E < 0 then the good is inferior.

Complementary goods typically replace one another in consumption. Thus, a decrease in demand for one good will typically increase the demand of the other good.

The question states that the price of one of the goods increased, which would lead to a decrease in its demand. If the demand of the other good increases as a result, than the two goods are likely to be substitute goods.

A private good is rival, which means that a person's consumption affects another person's consumption of the good, and excludable, which means that a person can prevent another person from consuming the good. Among the choices here, the only one that meets both criteria is the candy bar, which is both rival and excludable.

In terms of individual income and wealth, sales tax imposes a greater burden on the poor than the rich. One's consumption of taxable items typically does not increase as fast as one's income. Thus, lower-income individuals spend a larger portion of their income and wealth than higher-income individuals.

When not restricted by government or laws, monopolists will typically try to maximize their profit by producing fewer goods and selling them at higher prices than would be the case in a perfectly competitive market. The lack of competition allows them to charge higher prices without the threat of a competing firm driving down prices.  

Marginal cost is the increase in the total cost of production to produce one additional unit. In this case, we want to determine the marginal cost of producing the fourth good. The total cost for producing three goods is 26 and the total cost for producing four goods is 29. Because total cost increases by 3, 3 is the fourth good's marginal cost.

The profit maximizing quantity for the production of goods is the level at which marginal cost equals marginal revenue. This table allows us to easily determine the marginal cost of producing the nth good, but it does not give any information about the marginal revenue associated with selling th nth good (i.e. market price of the good).

Opportunity cost is defined as the value of the best alternative that must be forgone in order to pursue a certain action. In this case, the best alternative to watching TV is babysitting, for which Hank would have been paid $7. Thus, the opportunity cost of watching TV is $7 for Hank.

Since he chooses to watch TV, the personal benefit associated with watching TV must be greater than $7 for Hank. 

Comparative advantage refers to the ability to produce goods at a lower marginal/opportunity cost than another party. Even if one party is better than the other at the production of all goods (absolute advantage), both parties will still gain by trading with each other because of comparative advantage. Thus, in this case, California must have the comparative advantage in producing strawberries, while Iowa must have a comparative advantage in producing corn.  While the two states may or may not have absolute advantages, we have no way of knowing with the information given.  More importantly, the question states that the advantage is based on opportunity costs.  Absolute advantage has nothing to do with this.