Final answer:
Rebecca's gross income is $425, which comes from interest income of her bank savings. Since the interest from tax-exempt bonds is not taxed, and her income is below the threshold, she does not need to file a tax return.
Step-by-step explanation:
Rebecca's gross income consists solely of her interest income because the interest from tax-exempt municipal bonds is not subject to federal income tax. Therefore, her gross income is $425, which is the interest from her bank savings account. As she only has one source of taxable income and it is below the requirement for filing a tax return, especially considering her age and dependent status, Rebecca does not need to file a tax return. Answering the student's question, the correct choice would be: Gross income is $425, and she does not need to file a tax return.