Final answer:
Debbie's adjusted gross income is most likely $200,000, which is just her taxable interest income, assuming her Social Security benefits are not taxable.
Step-by-step explanation:
The student asked about Debbie's adjusted gross income (AGI) given her income sources. To determine the AGI, one must sum up all taxable income sources. Debbie has $200,000 in taxable interest and $20,000 in Social Security benefits. However, only a portion of Social Security benefits may be taxable, depending on the provisional income calculation which isn't provided here. If we assume all the Social Security benefits are tax-free, Debbie's AGI would be her taxable interest only, which is $200,000. If a portion of Social Security is taxable, the AGI would be higher but without additional information, an exact figure cannot be determined. Since the choice that represents $200,000 is an option (4), we can consider that as the most accurate answer given the lack of information on the taxation of the Social Security benefits.