Choice "D" is correct. The payback method typically ignores the time value of money and computes the number of years it will take for cash flows to equal (pay back) the initial investment.
Choice "b" is incorrect. The discounted payback method would take the time value of money into account.
Choice "c" is incorrect. The internal rate of return computes an expected rate of return and considers the time value of money.
Choice "a" is incorrect. The net present value method computes the amount by which an investment exceeds discounted cash flows or vice versa. The net present value method measures dollars, not years, and considers the time value of money.