Answer:
A. DNA is being transcribed into mRNA
Step-by-step explanation:
The process being diagrammatically described in this question portrays TRANSCRIPTION, which is the process whereby a mRNA molecule is synthesized using the information in a DNA template.
According to the diagram in this question, the DNA located in the nucleus is indicated by the blue strand. The mRNA transcript being produced is indicated by the red strand and can be seen leaving the nucleus.