13. Which of the following descriptions of CRISPR-Cas system is INCORRECT ? (A) CRIPSR is like an immune system in the bacteria to invade pathogen infections (B) It is applied potentially to edit germline cells for gene therapy (C) Cas9 targets a specific DNA sequence to make a cut across both strands of the DNA via a IncRNA (D) Off-target is the biggest issue that should be considered as CRISPR is used in gene therapy