When Comparing Two Projects with Different Lives, Why Do You

When comparing two projects with different lives, why do you compute an annuity with an equivalent present value (PV) to the net present value (NPV) ?

A) to ensure that cash flows from the project with a longer life that occur after the project with the shorter life has ended are considered
B) to reduce the danger that changes in the estimate of the discount rate will lead to choosing the project with a shorter timeframe
C) so that the projects can be compared on their cost or value created per year
D) so that you can see which project has the greatest net present value (NPV)