How many operons are present in the $nif$ gene cluster of $Klebsiella$ $pneumoniae$?

Consider the following statements of gene regulation and select the correct statements $:$
$(A)$ Expression of genes is regulated by metabolic,physiological,or environmental conditions.
$(B)$ Galactose can act as an inducer for the lac operon.
$(C)$ The operator region is adjacent to the promoter elements in most operons.
$(D)$ In the lac operon,lactose is transported into the cell through the action of permease.
$(E)$ Regulation of the lac operon by a repressor is referred to as positive regulation.

What does the $i$ gene encode in the $lac$ operon?

Which organism was used by Beadle and Tatum to propose the one gene-one enzyme hypothesis?

The activity of structural genes is controlled by.....

Which of the following enzymes increases the permeability of the bacterial cell to lactose?