Unbiased Denominator for Issuer Survival Study

You want to estimate the default frequency of bonds issued in 2018. Which denominator is the least survivorship-biased?

A. Only bonds still outstanding in 2026. B. Only bonds that traded in the last month. C. All bonds issued in 2018, including those that matured or defaulted later. D. Only bonds that are currently eligible for a benchmark index.

Give the best choice.