The tiny South Pacific island country of Maroji produces a lot of milk and milk-based products. To protect this industry, Maroji mandates that only designated trading companies can import cheese, each of which is allocated the right to import a maximum number of pounds of cheese each year. By doing this, Maroji controls the amount of imported cheese. This is an example of a(n)

a. import quota
b. import duty
c. import tariff
d. subsidy
e. local content requirement