Let's discuss interest rate risk. Which of the following bonds has the greatest interest rate risk? Why?

1. 10-year $100 annuity

2. 10-year, $1,000 face value, zero coupon bond

3. 10-year, $1,000 face value, 10% coupon bond with annual interest payments

4. 10-year, $1,000 face value, 10% coupon bond with semi-annual interest payments