The correct answer is A. Nucleus.
A nucleus is a membrane-bound organelle found in eukaryotic cells. It contains the cell’s genetic material, which is organized into chromosomes. The nucleus is responsible for controlling the cell’s activities and for regulating its growth and division.
DNA is a molecule that contains the genetic information of an organism. It is found in the nucleus of eukaryotic cells and in the cytoplasm of prokaryotic cells. DNA is made up of two strands of nucleotides that are twisted together in a double helix. The sequence of nucleotides in DNA determines the organism’s genetic code.
Cytoplasm is the jelly-like substance that fills the cell. It contains organelles, which are small structures that carry out specific functions in the cell. Cytoplasm is also the site of many chemical reactions that take place in the cell.
The cell membrane is a thin, flexible layer that surrounds the cell. It protects the cell from its environment and allows nutrients and waste products to pass in and out of the cell.
All of these structures are important for the cell’s function, but only the nucleus is specific to eukaryotic cells.