Final answer:
The discrepancy between Alabama's state sales tax and the average combined sales tax arises from higher local taxes in places such as Jefferson County and Montgomery City. Mobile County and Huntsville City also contribute to this disparity due to their local taxes.
Step-by-step explanation:
The disparity between Alabama's state sales tax rate and the average combined tax rate is due to additional local sales taxes imposed by certain counties and cities on top of the state sales tax. Counterintuitively, the option listing Birmingham County is incorrect, as Birmingham is a city within Jefferson County, and Montgomery is a city, not a county. As of the knowledge cutoff in early 2023, Jefferson County, which includes the city of Birmingham, and Montgomery, which is located in Montgomery County, typically have higher combined local and state sales tax rates compared to the rest of the state.
Similarly, Mobile County and the city of Huntsville in Madison County also impose higher local sales taxes. Madison County and the city of Hoover, which is located in Jefferson County, also contribute to the disparity with their local sales taxes. Therefore, Alabama's localities with additional sales taxes create a diverse landscape for tax rates within the state.