6. How often do living organisms make new cells? A. Never B. Sometimes C. Frequently D. Constantly

The correct answer is: **D. Constantly** **Explanation:** Living organisms continuously produce new cells through the process of **cell division**, primarily **mitosis**. This ongoing process ensures growth, tissue repair, and replacement of cells that are lost or damaged. For example: - **Humans:** Skin cells, blood cells, and cells lining the digestive tract are replaced regularly. - **Plants:** Cells in areas like the tips of roots and shoots are constantly dividing to support growth. - **Single-Celled Organisms:** Even microorganisms like bacteria reproduce continuously under favorable conditions. While the rate of cell division can vary between different organisms and different types of cells within an organism, the production of new cells is a **constant and essential process** for maintaining life.