Concept:The principle of certainty requires that a tax system clearly informs the taxpayer about the amount, time, and method of payment.Explanation:This principle ensures that every taxpayer knows exactly what to pay.It also states when the tax should be paid.It further makes clear how the tax should be paid.This removes confusion and makes tax administration transparent and predictable.The option that matches this description is the principle of certainty.Answer:D. Principle of certainty