The elasticity of demand along the demand curve shown in the above figure is constant and equal to 1. Thus

Which one of the following statements best describes the future of global freshwater supplies?

a. Water shortages are likely to become less frequent in both developed and developing countries b. Water shortages are likely to become less frequent in developing countries but more frequent in developed countries c. Water shortages are likely to continue at present rates in both developing and developed countries d. Water shortages are likely to increase, mainly in developed countries e. Water shortages are likely to increase, mainly in developing countries

Opportunity costs:

a. only include explicit costs paid out-of-pocket b. never involve costs paid out-of-pocket. c. may or may not involve costs paid out-of-pocket. d. are always measured in terms of time.