Country a is an extremely efficient producer of tin. however, its climate and terrain makes it difficult to produce corn. according to the theory of comparative advantage, country a should:

Theory of comparative advantage states that a country has a comparative in a production of certain commodities if the opportunity cost of producing these commodities is lower than the other countries.

Here, it is given that country A is a efficient producer of tin and there are some difficulties in producing corn. So, country A have to concentrate on the production of Tin and purchase the corn from any other efficient producer.