Please select the correct answer $($five points$)$:

Removal of endogenous TCR genes and the PD$-1$ gene using CRISPR $-$Cas$9$ ribonuclease protein complexes followed by the addition of external TCR genes specific for tumor antigens, results in CRISPR$-$edited T cells expressing both the endogenous TCR genes and the external TCR cells which recognize the tumor antigen, and in the elimination of the PD$-1$ gene product.

$0$

Removal of endogenous TCR genes and the PD$-1$ gene using CRISPR $-$Cas$9$ ribonuclease protein complexes followed by the addition of external TCR genes specific for tumor antigens, results in CRISPR$-$edited T cells expressing the external TCR cells which recognize the tumor antigen, and in the elimination of the PD$-1$ gene product.

Removal of endogenous PD$-1$ gene cannot be effectively accomplished from T cells, using CRISPR$-$Cas$9$ ribonuclease protein complexes.