What does '$2$' represent in the given figure?

In eukaryotes,the regulation of gene expression could be exerted at $:-$
$(I)$ Transcriptional level (formation of primary transcript)
$(II)$ Processing level (regulation of splicing)
$(III)$ Transport of $\text{mRNA}$ from nucleus to the cytoplasm
$(IV)$ Translational level
Choose the correct order for given statements $:-$

How is the $lac$ operon regulated by the repressor?

At which level is gene expression regulated in the $lac$ operon of $E. coli$?

In the Operon concept,the regulator gene regulates chemical reactions in the cell by:

In a negative operon,