Other things equal, which of the following bonds has the highest interest rate risk? (Hint: you do not need to do any calculation; just do pair-wise comparisons to determine which one is more sensitive to interest rate changes.)

1. A 10-year, 10% coupon bond issued by the US Department of the Treasury.
2. A 10-year, 20% coupon bond issued by the US Department of the Treasury.
3. A 10-year, 20% coupon bond issued by Microsoft.
4. A 15-year, 10% coupon bond issued by Santander.
5. A 15-year zero-coupon bond issued by the Massachusetts State Government.