The correct answer is guide RNA.
CRISPR is a gene editing tool that is used to alter DNA in a very precise, easy and cheap way.
This tool consists of two main parts:
A guide RNA
Case9 (a DNA-cutting enzyme)
The guide RNA is designed to mirror the DNA of the gene that is going to be edited. Then the guide RNA partners with Cas9 and leads it to the DNA. After that Cas9 cuts the DNA.