Pls, how does a rna polymerase know what dna strand to use as a gene template in the transcription unit during transcription?

Only one strand of DNA is active during the transcription process. A promoter is a part of a DNA that starts the transcription of a particular gene. It is double-stranded, directional, and specific. The promoter itself is not transcribed but instead it aids in the process.

Anscolon cancer;