$i.$ 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 Jacque Monod.
$A\;\;;\;\;B\;\;;\;\;C$
$(i)$ $RNA$ can directly code for the synthesis of proteins
$(ii)$ It is very common process to synthesis $DNA$ from $RNA$
$(iii)$ $RNA$ is used as genetic material only in human
$(iv)$ One polynucleotide chain is present in $RNA$