Which of the following statements about deductions is true?

Deductions can indeed be temporary and vary yearly, which is the essence of the correct answer. Tax laws and regulations change frequently, and different deductions may be available from year to year based on current legislation or the taxpayer's situation. For instance, certain deductions may be limited to specific tax years or may only be applicable when particular conditions are met, such as changes in mortgage interest deduction rules or an expansion of qualified educational expenses. This variability reflects the evolving nature of tax policy and individual taxpayer circumstances.

The other statements do not hold true for the general tax deduction framework. For example, saying that deductions increase the tax amount owed contradicts the fundamental purpose of deductions, as they are meant to lower taxable income and, consequently, the tax liability. Also, the notion that all deductions must be standard and cannot be itemized is incorrect, as taxpayers can choose between standard and itemized deductions based on what is most beneficial for their financial situation. Finally, deductions are not exclusive to self-employed individuals; they apply to all taxpayers subject to certain criteria, including those with wages, salaries, or various forms of taxable income.