Final answer:
The RNA in a cell is created through transcription, a process where RNA polymerase constructs RNA molecules from a DNA template.
Step-by-step explanation:
All of the RNA in a cell is made by the process of transcription. During transcription, an enzyme called RNA polymerase uses a DNA template to synthesize RNA. This process includes three types of RNA: messenger RNA (mRNA), transfer RNA (tRNA), and ribosomal RNA (rRNA). While DNA replication copies the entire DNA molecule, transcription only copies a specific gene or group of genes into RNA. The central dogma of molecular biology explains that genetic information flows from DNA to RNA to protein.
In summary, transcription is responsible for creating RNA from DNA, and then the translation process synthesizes proteins using the mRNA template. Therefore, the correct answer to the question is A. transcription.