Which of the following factors is fixed in the long run?

Ascertaining whether or not a regressor is strictly exogenous or exogenous ultimately requires all of the following with the exception of

A) economic theory. B) institutional knowledge. C) expert judgment. D) use of HAC standard errors.

In the supply-and-demand diagram of the market for peanut butter, the equilibrium point has moved up and to the right. What could have caused this?

A) a fall in the price of peanuts B) a rise in the price of peanuts C) a rise in income, assuming that peanut butter is an inferior good D) a shift in preferences toward peanut butter E) none of the above