In the past five years, the percentage of money spent on discovering renewable yet expensive sources of energy has decreased. An increasing amount of money is being spent on developing nonrenewable resources, which are quite inexpensive to obtain. Regrettably, the nonrenewable resources have proven to be impracticable for daily use. Clearly, less money is being spent on practicable energy sources than was being spent five years ago. Which one of the following, if true, allows the conclusion above to be properly drawn? ['Most of the money spent on developing renewable resources came from private donors.', 'The total investment in all energy resources is at an all time high.', 'The cost of nonrenewable resources is expected to rise in the next five years.', 'The total amount of money spent on developing energy resources has slowly declined over the past five years.']