Which of the following is not a component of the $Operon$ model?

When do bacteria $NOT$ produce $\beta$-galactosidase?

Select the two correct statements out of the four $(i-iv)$ statements given below about the lac operon.
$(i)$ Glucose or galactose may bind with the repressor and inactivate it.
$(ii)$ In the absence of lactose,the repressor binds with the operator region.
$(iii)$ The $z$-gene codes for permease.
$(iv)$ This was elucidated by Francois Jacob and Jacques Monod.
The correct statements are:

During lactose metabolism in $E. coli$,the repressor protein binds to the ...........

In the $lac$ operon,which molecule binds to the promoter site?

When does $lac$ operon in $E. coli$ become "switched on"?