Which of the following acts as a substrate for $RNA$ polymerase enzymes?

......... acts as a template.

Given below are two statements, one is labelled Assertion $(A)$ and the other is labelled as Reason $(R)$.
Assertion $(A) :$ In eukaryotes, primary transcripts $(hnRNA)$ contain both exons and introns, and introns are non-functional.
Reason $(R) :$ In bacteria, the $mRNA$ does not require any processing, and transcription and translation take place in the same compartment.
In the light of the above statements, choose the most appropriate answer from the options given below $:$

Which of the following is not a part of a transcription unit?

$A$ segment of $DNA$ coding for a polypeptide,the structural gene in a transcription unit is called . . . . . . .

Identify the $INCORRECT$ statement with reference to transcription unit.