Final answer:
An individual with a $40,000 AGI contributing $2,000 to a retirement account is eligible for the saver's credit, assuming they meet all other qualifications for the credit.
Step-by-step explanation:
The taxpayer who is eligible to take the saver's credit, provided they meet the income restrictions, is the individual with $40,000 AGI who is contributing $2,000 to a retirement account. This is because the saver's credit, also known as the retirement savings contributions credit, is designed to provide a tax break to low- and moderate-income taxpayers who are saving for retirement. To qualify for the saver's credit, individuals must meet certain income limits, be at least 18 years old, not be a full-time student, and not be claimed as a dependent on another person's tax return. As the provided options do not include any details to disqualify the taxpayers based on these criteria besides income restrictions, we are focusing on the income aspect alone. In general, incomes below certain thresholds (which vary each year and are adjusted for inflation) for single, married filing jointly, or head of household taxpayers are eligible for the credit.