The tax credit that is available to Savannah would be D. Child and Dependent Care Credit for Disabled Dependents
Child and Dependent Care Credit for Disabled Dependents, is available to Savannah because she provides 100% support for her permanently and totally disabled brother, Brock, who lived with her for more than 6 months in the U.S. This credit is specifically designed to provide financial relief to individuals caring for disabled dependents.
Child and Dependent Care Credit is generally for expenses related to the care of dependents while the taxpayer is at work, but it doesn't apply here because Savannah is not incurring any childcare expenses for Brock.
Options are:
Child Tax Credit
Child and Dependent Care Credit
Earned Income Tax Credit
Child and Dependent Care Credit for Disabled Dependents