Answer:
Option (d).
Step-by-step explanation:
The well defined nucleus is absent in prokaryotes whereas the well defined nucleus covered with nuclear envelope is present in eukaryotes. The site of replication and transcription is the nucleus in the living organism.
The nucleus contains the double membrane structure. Outer membrane and inner membrane covers the nucleus. Nucleus also contains the nuclear pore through which molecules can move inside and outside of the nucleus and the cytoplasm.
Thus, the correct answer is option (d).