Answer: c. 100%
Step-by-step explanation:
When contributing to Traditional Individual Investment Accounts (IRAs), you are allowed to deduct these contributions either fully or partially from your taxable income which means that you get to pay less taxes.
When you retire however, and the retirement distributions begin to come in, those distributions will be subject to taxes because you didn't pay taxes on them when you were contributing to the IRA. If you fully deducted the contributions, that means your IRA distributions would have to be fully taxable as well.