Concept: The canon of certainty ensures that taxes are fixed, clear, and not left to the arbitrary discretion of the government.
Explanation:The canon of certainty is one of Adam Smith's canons of taxation.
Under this canon, every taxpayer must clearly know the amount of tax to be paid, the time of payment, and the method of payment.
When these details are established by law, the government cannot change tax burdens at will or act unfairly toward citizens.
This protects people from arbitrary taxation because the tax system becomes predictable and rule-based rather than dependent on the mood of tax officials.
The other canons are different: elasticity refers to how tax revenue adjusts to income, flexibility refers to changing tax rates easily, and economy refers to minimising the cost of tax collection.
Therefore, protection from arbitrariness comes from certainty, not from those other canons.
Answer: D. certainty