Empty spaces within cytoplasm that contain waste materials or secretions formed by the cytoplasm.

• A. Nucleolus
• B. Cytoplasm
• C. Granules
• D. Vacuoles

Answer: (D)

The concept here is storage compartments within the cytoplasm. Vacuoles are membrane-bound sacs that form inside the cytoplasm to hold substances. They act as spaces where waste materials or secretions produced by the cell can be stored or transported. In plant cells, a large central vacuole stores water and helps maintain turgor pressure, while in animal cells vacuoles are smaller but serve the same storage role. They often appear as clear or empty spaces in prepared slides because their contents can be removed during fixation, yet in living cells they contain fluid and material. The other terms don’t describe these storage spaces: the nucleolus is a structure inside the nucleus involved in making ribosomes; cytoplasm is the entire internal content of the cell outside the nucleus; granules are small particles or inclusions, not empty storage spaces.