Cells are the basic structural and functional units of life. This statement is considered a scientific theory because: A. Different kinds of cells have different structures and functions. B. Every living thing observed so far consists of one or more cells. C. The structure of a skin cell enables it to perform its functions. D. All cells can exchange matter and energy with their surroundings.

The statement "Cells are the basic structural and functional units of life" is considered a scientific theory because: B. Every living thing observed so far consists of one or more cells.

Explanation:

• Scientific theories are explanations or models based on extensive observations, experiments, and evidence that have been repeatedly tested and confirmed through scientific inquiry.
• The cell theory, which states that cells are the fundamental units of life, is a well-established scientific theory supported by extensive empirical evidence.
• Option B reflects one of the fundamental principles of the cell theory: the observation that every living organism that has been studied consists of one or more cells. This observation is a key component of the evidence supporting the cell theory.
• Options A, C, and D describe aspects related to cells but do not directly address the foundational evidence supporting the cell theory, which is the consistent observation of cells in living organisms, thus making them less directly relevant to the establishment of the cell theory as a scientific theory.