Choice "D" is correct. A decrease in taxes for each year for four years causes increases in cash flow over a greater period of time than other alternatives and, therefore, a greater present value than any of the alternatives. Choice "a" is incorrect. A decrease in cash outflow would improve present value but this alternative suggest a three rather than four year benefit. Choice "a" is not as beneficial to present value as choice "D".Choice "b" is incorrect. A $100 increase in disposal value at the end of four years would increase present value but it would not increase present value as much as choice "D", a four-year annuity in the same amount each year.Choice "c" is incorrect. An increase in cash inflow would improve present value but this alternative suggests a three, rather than four, year benefit. Choice "c" is not as beneficial to present value as choice "D".