Final answer:
The most complete model of cellular structures present in all living cells must include the plasma membrane, cytoplasm, and genetic material (DNA), as these are common essential components of all cells.
Step-by-step explanation:
The most complete model showing the cellular structures present in all living cells would include those structures that are essential and common to all cells. At the core of cell structure is the plasma membrane, which encloses the cell and serves as a barrier controlling the movement of substances in and out of the cell. Inside the plasma membrane is the cytoplasm, a gel-like substance where all the organelles are suspended. In addition, all cells contain genetic material, primarily DNA, which dictates cellular function and heredity. While other structures like mitochondria, endoplasmic reticulum, and chloroplasts are found in many cells, they are not present in all cells. Therefore, the most complete model of cellular structures present in all living cells would feature the plasma membrane, cytoplasm, and DNA.