In Order for a Preferential Trade Agreement to Be Legal

In order for a preferential trade agreement to be legal under international trade rules:

A) it must reduce trade barriers on all agricultural products among member countries.
B) it must reduce trade barriers on a substantial proportion of trade among the member countries.
C) it must reduce restrictions on the mobility of labor and capital among member countries.
D) it must provide a common external tariff for member countries.
E) All of the above