In the figure showing gene expression , what should replace label b ?

The correct answer is C. Translation.

The given figure is the scheme of the gene expression. It provides the flow of genetic information from a DNA sequence to a protein synthesis inside cells. This process of flow of genetic information from DNA to RNA is called transcription and the process of flow of genetic information from RNA to protein is called translation.

Thus in given figure label A is to be replaced by transcription and label B is to replace by translation.

the correct answer is d