According to the cell theory, which statement is true?

The cornerstone of cell theory is the idea that all living organisms are composed of one or more cells. This fundamental principle emphasizes that cells are the basic unit of structure and function in all living things. Whether it's a single-celled organism like bacteria or a complex multicellular organism like humans, they all rely on cells for their structure and processes. This concept reinforces the importance of cells in biology and underscores their role as the building blocks of life.

The other statements do not align with this core idea. Spontaneous generation—cells forming from non-cellular material—has been disproven by scientific research. Similarly, stating that cells are created solely through chemical reactions overlooks the biological processes of cell division, and claiming that cells are the largest unit of life fails to recognize that they are, in fact, the smallest unit of life capable of sustaining processes like metabolism and reproduction. Without the foundational principle that all living organisms are made up of cells, the understanding of biology would be fundamentally flawed.