What are the elements of international trade?

I- Customs Regime: Rules that regulate the operation of CUSTOMS services, which are responsible for controlling and registering the import and export of goods from a country.
II- Drawback: It is a promotion instrument for exports, through which the exporter is reimbursed for the value of the taxes on imported goods that are incorporated into export goods or for goods that are returned in the same condition.
III- Barriers: They are general regulations imposed by governments limiting international trade to protect national producers. These barriers can take the form of tariffs, quotas, import deposits, restrictions on the use of import permits, or severe limitations on quality, health, and safety standards.
IV- Tariff Barriers: They are regulations with the imposition of tariffs (import taxes), with the purpose of protecting national production, raising the selling price of foreign goods entering the country.
a) Only I, II, and III are correct.
b) Only II, III, and IV are correct.
c) Only I, III, and IV are correct.
d) I, II, III, and IV are correct.