Which one of the following is not a sub-index of the World Bank's Ease of Doing Business Index?

Option (a) is the correct answer because "Maintenance of law and order" is a general governance function and is not one of the 10 specific regulatory parameters measured by the World Bank's Ease of Doing Business Index. While "Paying taxes" (Option b) might seem like a broad policy area, it is a core sub-index that tracks the administrative burden and costs of tax compliance for businesses. The question tests the candidate's ability to distinguish between specific business regulatory indicators and general socio-political stability factors.