"Diminishing returns" refers to the idea that

	a.	you add more units of a single input and output goes down.
	b.	you face economies of scale.
	c.	there's only so much of a good you can produce before a cheaper supplier enters the market.
	d.	You add more units of a single input,and output increases at a slower rate.

What might be the best way to encourage the invention of a cure for malaria?

	a.	announce a big prize for an effective malaria cure--this would enable rich and poor countries to access a cure the most quickly
	b.	send out grants to university biomedical departments to do basic research on insect-spred diseases
	c.	issue patents to the companies that find solutions
	d.	allow the free market to find a cure.

A binding price floor in labor markets could account for why there are people unemployed. But what could explain a binding price floor?

	a.	the union wage
	b.	the minimum wage
	c.	the efficiency wage
	d.	all of these could be explanations for a binding price floor.