Final answer:
For a zero coupon bond, the duration is equal to its time to maturity. Thus, the duration of a 5-year zero coupon bond is exactly 5 years.
Step-by-step explanation:
The question pertains to the duration of a 5-year zero coupon bond. Duration is a measure of the sensitivity of the price of a bond to changes in interest rates and is also considered a measure of the bond's interest rate risk. For a zero coupon bond, the duration is equal to its time to maturity since there are no intermediate cash flows to consider.
In the case of a 5-year zero coupon bond, the duration is equal to its time to maturity because the only cash flow comes at the end of the bond's life. Therefore, the correct answer to the question 'What is the duration of a 5-year zero coupon bond?' is b) 5.0.