Answer: d. internal rate of return
Step-by-step explanation:
The Internal Rate of Return can be a very useful method for measuring the viability of a product because it takes into account the magnitude and timing of cashflows when it discounts it to the current period to find out if it will lead to a higher NPV than zero.
The other methods have their limitation. The payback period does not take into account the entire lifetime but rather stops as soon as the project pays back and the other two do not take into account the timing of the cashflows.