Which of the following is true of an economy's production possibilities
curve?

It shows the combinations of any two resources that can be used to produce an
efficient level of output.

It shows the alternative combinations of goods that can be produced by fully
employing scarce resources.

It must be a straight line when all resources are fully employed.

It is bowed in (convex to the origin) because of changing levels of technology

It is bowed out (concave to the origin) when marginal opportunity costs are
constant