When Using the Most Favored Nation Principle in International Trade

When using the most favored nation principle in international trade, this means that:

A) we prefer a foreign country's production to domestic production.
B) the lowest MFN negotiated tariff rate would apply to all WTO members countries.
C) the lowest negotiated tariff rate would apply to some countries.
D) the countries have come close to a free trade agreement.
E) we apply MFN only to friendly countries.