Answer:
D. srp
Step-by-step explanation:
The protein-RNA macromolecule involved in sorting is D. srp (signal recognition particle). The signal recognition particle is a ribonucleoprotein complex that binds to the signal peptide of newly synthesized proteins in the cytosol and targets them to the endoplasmic reticulum for membrane insertion. It consists of both protein and RNA components, making it a protein-RNA macromolecule.