Which of the following probably violate the rules of the WTO?

a. A country’s government places a tax on domestic production to reduce pollution caused by this production.

b. A country’s government prohibits imports of foreign goods produced using production methods that would violate this importing country’s environmental protection laws.

c. A country’s government places a tax on domestic consumption of goods (both imported and domestically produced) to reduce pollution caused by this consumption.

d. A country’s government restricts imports of a good to reduce pollution caused by consumption of this good.