The correct answer is D. All of the above.
Normative economics is the branch of economics that deals with value judgments and opinions about what the economy should be like. It is concerned with the desirability of economic outcomes, rather than with their causes or consequences.
The incidence of a tax is the economic burden of the tax, which may fall on different people than those who are legally liable for the tax. For example, a sales tax may be legally imposed on businesses, but the economic burden of the tax may fall on consumers in the form of higher prices.
The effect of a tax on incentives to work is the impact of the tax on people’s willingness to work. A tax that increases the cost of working, such as an income tax, may reduce people’s incentive to work.
The “fairness” of a tax is a subjective judgment about whether the tax is fair or unfair. There are many different theories of fairness, and people may disagree about whether a particular tax is fair.
All of these aspects of taxation involve normative economics, because they are concerned with value judgments about what the economy should be like.