federal income tax question

Mark for follow up Question 12 of 12. Most tax planning suggestions are given during the preparation of a prior-year return. The suggestions enable taxpayers to plan for the future but do not affect the outcome of the return currently being filed. Which process CAN reduce tax liability on the prior-year return that is being prepared as the advice is given? Completing Step 4 (optional), Other Adjustments on the 2020 Form W-4, Employee's Withholding Certificate O Purchasing savings bonds. Completing a Form 2210, Underpayment of Estimated Tax by Individuals, Estates, and Trusts. Contributing to a Coverdell Education Savings Account OOOO Mark for follow up Back Save / Return Later Summary Mark for follow up Question 12 of 12. Most tax planning suggestions are given during the preparation of a prior-year return. The suggestions enable taxpayers to plan for the future but do not affect the outcome of the return currently being filed. Which process CAN reduce tax liability on the prior-year return that is being prepared as the advice is given? Completing Step 4 (optional), Other Adjustments on the 2020 Form W-4, Employee's Withholding Certificate O Purchasing savings bonds. Completing a Form 2210, Underpayment of Estimated Tax by Individuals, Estates, and Trusts. Contributing to a Coverdell Education Savings Account OOOO Mark for follow up Back Save / Return Later Summary