Explain the difference between fixed costs in the short run and fixed costs in the long run

When economists talk about the gains from trade they mean that

A) no one ever gets hurt by trade. B) the benefits of trade outweigh the losses. C) business firms benefit from trade but not necessarily individuals. D) trade increases government revenue through taxes on imports. E) economic restructuring is usually quick and painless.

The assumption that the marginal product of labor decreases as the labor input increases implies that

A) output decreases as the labor input increases. B) the wage increases as the labor input increases. C) the production function is concave. D) the production function shifts upward.