Citizens are protected from the government's arbitrariness in taxation by the canon of

Step 1: Analyze the question The question asks which canon (principle) of taxation protects citizens from arbitrary action by the government. The key word is "arbitrariness," meaning the government taxing people according to its whim.

Step 2: Recall the canons of taxation (Adam Smith's and others)

• Equity/Fairness: tax should be based on ability to pay.
• Certainty: the taxpayer should know how much to pay, when to pay, and how to pay. It should not be arbitrary.
• Convenience: tax should be collected at a time and in a manner convenient to the taxpayer.
• Economy: the cost of collecting the tax should be low compared with the revenue.
• Elasticity/Flexibility: the tax system should be able to yield more or less revenue as government needs change.
• Productivity: the tax should generate enough revenue.

Step 3: Match the concept to the options

• A. Elasticity: concerns the ability of revenue to expand as needs grow. It has nothing to do with arbitrariness.
• B. Flexibility: concerns adjusting taxes to changing circumstances. It is not a protection against arbitrariness.
• C. Economy: concerns low collection costs.
• D. Certainty: requires that the rate, time, and method of payment be clearly defined and known in advance. This means the government cannot impose taxes arbitrarily, so citizens are protected.

Step 4: Answer

Exam tip: Link keywords to canons. "Arbitrary" or "known in advance" points to certainty. "Cost of collection" points to economy. "Ability to pay" points to equity. "Time and manner of payment" points to convenience.