The correct answer is: C. both (a) and (b)
Value Added Tax (VAT) is an indirect tax levied on the value added to goods and services at each stage of production and distribution, from the primary produce to the final consumer. The seller is liable to pay VAT to the government on the selling price of goods or services, but can claim back the VAT that they have paid on the goods and services that they have purchased.
Option A is correct because VAT is an indirect tax. Indirect taxes are taxes that are levied on goods and services, and are paid by the consumer, but are collected by the seller on behalf of the government.
Option B is correct because VAT is calculated on the selling price. The selling price is the price at which the goods or services are sold to the final consumer.
Option C is the correct answer because VAT is both an indirect tax levied at each stage of production and distribution, and a tax calculated on the selling price.