Which part of the cell supervises its activity?

The nucleus is often referred to as the control center of the cell because it houses the cell's genetic material (DNA) and coordinates various activities, including growth, metabolism, and reproduction. It regulates gene expression, allowing the cell to respond to various signals and environmental changes. By controlling the production of proteins and other molecules, the nucleus plays a crucial role in maintaining the cell's identity and functionality.

Mitochondria are primarily responsible for producing energy in the form of ATP through cellular respiration. While they contribute significantly to the cell's energy needs, they do not supervise the cell's overall activities.

Cytoplasm is the jelly-like substance that fills the cell and contains the organelles, but it does not direct the cell's functions. Instead, it serves as the medium for biochemical reactions and supports the cellular structures.

Ribosomes are the sites of protein synthesis, translating messenger RNA into proteins. While essential for producing the proteins necessary for various cellular functions, they do not manage the cell's overall activities.

Thus, the nucleus is correctly identified as the part of the cell that supervises its activities, making it the most accurate answer to the question.