Which of the following is NOT one of the three main parts of a cell?

The correct choice is the cell wall because it is not one of the three main parts of a cell. The three primary components that make up most cells are the nucleus, cytoplasm, and plasma membrane.

The nucleus serves as the control center of the cell, housing the genetic material (DNA) and coordinating activities such as growth, metabolism, and reproduction. The cytoplasm is the gel-like substance within the cell, where various cellular processes occur and where organelles are suspended. The plasma membrane is the protective barrier that surrounds the cell, regulating the movement of substances in and out of the cell.

While the cell wall is found in plant cells, fungi, and some bacteria, it is not considered one of the three main parts of a cell. Instead, it functions as an additional protective and structural layer outside the plasma membrane in those specific types of cells. This distinction is key in understanding cellular structure across different organisms.