Which one of these correctly defines equivalent taxable yield?

Multiple choice question.

The after$-$tax rate earned on either a taxable or nontaxable bond.

The pretax rate required on a taxable bond to yield the same rate as a muni bond

The after$-$tax rate needed on a corporate bond to equal the after$-$tax rate on a muni bond

The pretax rate needed on a taxable bond to produce the same after$-$tax rate as a muni bond