In an Offer Curve Diagram with Country A's Export Good

Multiple Choice

In an offer curve diagram with country A's export good (country B's import good) on the horizontal axis and country B's export good (country A's import good) on the vertical axis, which one of the following events will shift or pivot country B's offer curve upward (or to the left) ?

A) increased demand by A for B's export good
B) technological improvement in A's export industry
C) imposition of a tariff by B
D) a change in tastes by B's consumers toward wanting more of A's export good And less of B's export good