Explanation

Option A is correct: Cas9 (CRISPR-associated protein 9) is an RNA-guided endonuclease enzyme derived from bacterial immune systems:

– In the CRISPR-Cas9 genome editing technology, Cas9 acts as a programmable pair of molecular scissors.
– Guided by a guide RNA (gRNA) sequence complementary to a specific genomic locus, the Cas9 enzyme creates precise double-strand breaks in target cellular DNA, allowing targeted deletion, modification, or insertion of genetic material.

Therefore, Cas9 is A molecular scissors used in targeted gene editing — Option A.