Hey there!
Option D would be correct.
Hope this helps, tell me if I am wrong!
I think it might be the second one sorry if I’m wrong
Your answer is D. Nucleotide
For the answer to the question above, I think that <span>the initial titer that has been done to her may have been done too early in the infection that detectable levels of antibody were not present yet so that's why they have to repeat it.</span>
The first word specifies the genus of the species.