Which of these statements about cells is true according to cell theory?

The statement that all living organisms contain one or more cells is a fundamental concept of cell theory. Cell theory, developed in the mid-19th century, outlines three primary principles:

1. All living organisms are composed of one or more cells.

2. The cell is the basic unit of life.

3. All cells arise from pre-existing cells.

This principle emphasizes the universality of cellular organization across all forms of life, from unicellular organisms like bacteria to multicellular organisms like plants and animals. The importance of this statement lies in understanding that cells are the basic building blocks of all living organisms, which serves as the foundation for biological sciences. Other options are misaligned with the tenets of cell theory; for example, cells can vary greatly in structure and function, cannot arise from non-cellular components, and do have the capability of reproduction.