When production is characterized by opportunity costs, the resulting production possibilities frontier will be a straight line.

The statement is correct. When production is characterized by constant opportunity costs, the resulting production possibilities frontier (PPF) will indeed be a straight line. Here's why:

1. The production possibilities frontier represents all possible combinations of two goods that a country can produce, given its resources and technology, while keeping efficiency at its maximum.

2. Opportunity cost is the cost of forgoing the next best alternative when making a decision. In this context, it's what we give up producing of one good, in order to produce more of the other good.

3. When opportunity costs are constant, it means that the resources are perfectly substitutable between the production of the two goods. In other words, resources can be switched from the production of one good to the other without any loss in efficiency.

4. This perfect substitutability of resources results in a constant trade-off between the production of the two goods, which is graphically represented by a straight line PPF.

5. On the contrary, if opportunity costs were increasing (meaning resources are not perfectly substitutable and efficiency is lost when reallocating them), the PPF would be concave to the origin (bowed outwards).

So, in summary, a straight line PPF is an indication of constant opportunity costs in production.