What makes ribosomal RNA useful as a molecular clock?

A- A large portion of the DNA ring is not vital to structure or function, allowing it to accumulate neutral mutations.

B- Its rate of mutation increases over time as organisms continue to evolve and differentiate from each other.

C- A slow mutation rate makes it useful for determining evolutionary relationships between ancient species.

D- It is only found in select organisms, making it easier to compare relationships between species that have it.