这题为什么选A（L）区域？

问题如下：

Question

The gain in government revenues arising from the imposition of the tariff is best described by area(s):

The diagram below shows the domestic demand and supply curves for a country that imports a commodity, where P_W is its world price and P_T is its domestic price after the imposition of a tariff.

选项：

A.L. B.J. C.K + M.

解释：

Solution

A is correct. With the imposition of the tariff, domestic supply will increase from Q₁ to Q₂, but domestic demand will fall from Q₄ to Q₃. The net amount imported will be Q₃ – Q₂. The change in government revenues is Area L, which is the rectangle (Q₃ – Q₂) × (P_T – P_W).

B is incorrect. It is the gain in producer surplus.

C is incorrect. It is deadweight loss.