Which of the following statements regarding bonds are least accurate?

1. A bonds YTM is the return an investor will earn if they reinvest all coupon payments at the expected internal rate of return and hold till maturity.
2. A bonds YTM is the return an investor will earn if they reinvest all coupon payments at the then current market rates and hold till maturity.
3. A debenture is typically backed by an asset that the bond holder can repossess if the debt is not paid.
4. A general obligation bond is backed by the taxing authority of the issuing municipality.