Why do researchers use rRNA in investigations of relationships between taxa that diverged hundreds of millions of years ago?

Option 3 DNA coding for rRNA changes relatively slowly.

Explanation:

The complete question is as follows:

Why do researchers use rRNA in investigations of relationships between taxa that diverged hundreds of millions of years ago?

rRNA is never the nucleic acid chosen for comparisons. rRNA cannot mutate. DNA coding for rRNA changes relatively slowly. rRNA mutates rapidly. rRNA is traditionally the nucleic acid chosen for recent comparisons.

rRNA is the ribosomal RNA which along with the ribosomal proteins forms the ribosomes which play an important role in protein synthesis. rRNA does not code for anything however, it is still the most abundant form of RNA found in most of the cells, covering for around 80% of the total RNA. The genes that code for rRNA are quite resistant to mutations and alterations and thus, the sequence of the rRNA is quite conserved. A reason for the conservation of the rRNA is that any alteration in its sequence makes it non functional. This key feature of the rRNA makes it useful for phylogenetic and taxonomical studies to investigate the relationship between organisms.