Contains all of the living substances of the cell, additionally carries out all the functions for cell expansion such as growth and replication.

• A. Nucleus
• B. Organ
• C. Cell Membrane
• D. Cytoplasm

Answer: (D)

The cytoplasm is the place where all living substances of the cell reside and where most growth- and metabolism-related processes take place. It fills the interior of the cell between the plasma membrane and the nucleus and contains the cytosol along with the organelles. This is where the chemical reactions that keep the cell alive occur, including energy production, protein synthesis, and other pathways needed for growth and expansion of the cell. The nucleus, while it stores genetic material and directs many activities, does not itself carry out the bulk of metabolism or growth. The cell membrane is just the boundary that controls what enters and leaves, not a site of metabolic activity. An organ refers to a structure made up of tissues in multicellular organisms—not a single cell component—so it doesn’t fit as the site of the cell’s living substances and growth functions. Hence, the cytoplasm best fits the description.