Economist: Ordinarily, when energy efficiency improves, less energy is used to satisfy the same needs. So presumably, if a country improves its energy efficiency, then ordinarily its energy consumption should decrease. Yet empirical data show that as a country' s energy efficiency increases, energy consumption there either rises or stays the same. Which one of the following, if true, most helps to explain the conflict between the economist's presumption and the empirical data?
A: When countries increase their energy efficiency, they usually sell their surplus of energy to other countries.
B: When countries increase their energy efficiency, more energy-efficient appliances are bought than appliances that are not energy efficient.
C: Causes other than increased energy efficiency can account for decreased energy consumption.
D: Increases in energy efficiency in a country are typically accompanied by the introduction of new energy-consuming products.
Choose A, B, C or D as your solution.
D