Which term best describes the basic internal structures of cells?

• A. Inclusions
• B. Nucleolus
• C. Organelles
• D. Rough endoplasmic reticulum

Answer: (C)

Organelles are the basic internal structures of cells, each organized to carry out a specific function that keeps the cell alive and functioning. They create the compartments and machinery for energy production, protein synthesis, packaging and trafficking, digestion, and more. The nucleolus, by contrast, is a distinct region inside the nucleus where ribosomal RNA is synthesized, so it’s not the general category for all internal cell structures. Inclusions are storage materials such as glycogen or lipid droplets that don’t define a functional compartment of the cell, and the rough endoplasmic reticulum is one particular organelle involved in protein synthesis with ribosomes on its surface. Because the question asks for the overarching term describing the cell’s internal components, organelles is the best fit.