Final answer:
The threshold for investment income that would disqualify a taxpayer from claiming the Earned Income Tax Credit (EITC) for 2021 is $3,650.
Step-by-step explanation:
The threshold for investment income that would disqualify a taxpayer from claiming the Earned Income Tax Credit (EITC) for 2021 is $3,650 (option b).
The EITC is a tax credit aimed at helping low-income workers and families. It provides financial assistance through the tax system by increasing the payment received for work.
However, if a taxpayer's investment income exceeds the threshold, they are not eligible for the EITC. This is because the EITC is designed to assist individuals and families with limited income.