In the Following Diagram, Offer Curve 0A₀ of Country a Is

Multiple Choice

In the following diagram, offer curve 0A₀ of country A is the free-trade offer curve, and the other four offer curves represent A's offer curves under four different tariff rates. Of these four other curves, only one of them can possibly be an offer curve which is associated with A's "optimum tariff." Which one?

A) 0A₁
B) 0A₂
C) 0A₃
D) 0A₄