Definitions/Explanation : Regulatorgene & Promotergene
 

$A$ : Single $DNA$ dependent $RNA$ polymerase catalyses transcription of all types of $RNA$ in all except bacteria.
$R$ : Structural genes in bacteria are monocistronic.

E.coli cells with a mutated $Z$ gene of the lac operon cannot grow in medium containing only lactose as the source energy because

$A$ : Lac operon exerts negative control only.
$R$ : The operator is occupied by aporepressor during regulation

Definitions/Explanation : Splicing & Operator gene