Which one of the following statements about $Agrobacterium \;Ti\; plasmid$ is $CORRECT$?

1. $Vir$ genes are located within the $T-DNA$ segment
2. Phytohormone biosynthesis genes are located outside the $T-DNA$ segment
3. Opine catabolism genes are located within the $T-DNA$ segment
4. Opine biosynthesis genes are located within the $T-DNA$ segment