Return $($IRR$)$ method is$/$are the most correct?

a$.$ The IRR is the discount rate that equates the NPV of a project with zero.

b$.$ The IRR method assumes that cash flows will be reinvested at the cost of capital.

c$.$ The IRR method generates three IRRs for a project if its cash flows change sign three times throughout its life.

d$.$ Both a and $lon$ are correct.

e$.$ Both b and c are correct.