A) Tax imposed upon all imported goods and services describes a trade tariff.
The tariff is a tax charged on goods purchased and service rendered between countries. This is a regulation that regulates foreign trade to protect domestic trade of one's country. They work hand in hand with exports and imports quotas. Tariff amount is either fixed or it varies.
In the case where it is fixed, it is normally a constant amount per a certain unit of goods or a constant percentage. If it is not fixed it means it is charged based on the price of the goods or services.