Which of the Following Statements About a Production Possibilities Curve

Which of the following statements about a production possibilities curve that is "bowed out" or concave to the origin is the most accurate?

A) It illustrates a trade-off in which the opportunity cost of a good is constant at all levels of production.
B) It illustrates a trade-off in which the opportunity cost of a good decreases with the level of its production.
C) It demonstrates the fallacy of composition.
D) It illustrates a trade-off in which the opportunity cost of a good increases with the level of its production.