Suppose that, in a Classical constant-opportunity-costs framework, country I can produce 15 units of wheat if it devotes all of its resources to wheat production and 45 units of clothing if it devotes all of its resources to clothing production. In a trading situation for this country, if the world price ratio is Pwheat/Pclothing = ⅓ (or Pclothing/Pwheat = 3), country I would
选项：

A:export wheat and import clothing.
B:export clothing and import wheat.
C:be indifferent to trade.
D:export either clothing or wheat and import either wheat or clothing – cannot be determined without more information.