What are the main components of the cell theory?

The correct answer emphasizes the fundamental principles that define the cell theory, which is a cornerstone of biological sciences. The cell theory states that:

1. All living organisms are composed of one or more cells.
2. The cell is the basic unit of life — meaning it is the smallest structural and functional unit of an organism.

3. All cells arise from pre-existing cells — highlighting that new cells are created through the division of existing cells.

These principles collectively illustrate the importance of cells as the basic building blocks of life and establish that life is a cellular process, reinforcing the interconnectedness of all living organisms through the cellular structure.

The other choices do not accurately reflect the established components of cell theory. For instance, stating that all cells are identical and that all living things are microscopic is misleading, as there is significant diversity among cells, and many organisms consist of macroscopic structures. The notion that cells can only reproduce sexually is incorrect, as cells can reproduce asexually as well through processes like mitosis. Lastly, the idea that cells are completely independent of their environment is inaccurate, as cells interact with their surroundings, which significantly influences their function and survival.