Step 1: Understanding the Question:
This question tests knowledge of CRISPR-Cas 9 applications.
Step 2: Detailed Explanation:
CRISPR-Cas 9 is used in gene therapy.
It allows precise editing of genes for therapeutic purposes.
It can correct genetic mutations in diseases.
Gene conversion (B): Not the primary use of CRISPR.
Gene donation (C): Not a standard term.
Gene regulation (D): CRISPR can be used for gene regulation (CRISPRi, CRISPRa), but the primary use is gene therapy.
Thus, CRISPR-Cas 9 is used in gene therapy.
Step 3: Final Answer:
Thus, CRISPR-Cas 9 is used in gene therapy, which corresponds to option (A).
[0.5cm]