The price index in the base year always equals_____

One explanation given in the video for the fluctuations of an economy's real growth rate around its potential growth rate is:

A. that there are often shocks to the planned level of spending. B. that there are often shocks to the money supply. C. that the potential growth is inaccurately calculated. D. that there are often shocks to the key growth factors

If an economy is efficient:

a. resources are still available to produce specific consumer goods that are more desirable. b. prices are the lowest they can possibly be. c. all goods are produced at their maximum price and quality. d. all opportunities to make people better off without making other people worse off have been exploited.