Final answer:
Terminal deoxynucleotidyl transferase (TdT) is responsible for introducing nucleotides to free 3' OH in a template-independent manner, particularly during the process of V(D)J recombination, which contributes to antibody diversity.
Step-by-step explanation:
What introduces nucleotides in a template-independent manner?
The molecule that introduces nucleotides in a template-independent manner to free 3' OH created upon cleavage of the interstrand hairpin is terminal deoxynucleotidyl transferase (TdT).
This enzyme is known for adding nucleotides to the ends of DNA molecules during the process of V(D)J recombination, which is fundamental in the generation of antibody diversity.
None of the other options listed (Artemis, RAG-1/2, XRCC4 with DNA ligase IV, or Ku 70 and Ku 80) introduce nucleotides in this manner.
Instead, they are involved in other aspects of the DNA repair, recombination, and joining processes.