Which of the following is not a limitation of the absolute and comparative advantage theories?
a) The theories assume that there are only two countries engaged in the production and consumption of just two goods.
b) The theories assume that there are no costs for transporting traded goods from one country to another.
c) The theories consider labor the only resource used in the production process.
d) The theories assume that specialization in the production of one particular good results in gains in efficiency.