Answer:
A. Cell theory.
Step-by-step explanation:
The image above shows salamander skin cells as viewed under a microscope. The activity occurring inside the rectangle best supports a scientific theory known as cell theory with respect to cell division.
A cell can be defined as the fundamental or basic functional, structural and smallest unit of life for all living organisms. Some living organisms are unicellular while others are multicellular in nature.
A unicellular organism refers to a living organism that possess a single-cell while a multicellular organism has many (multiple) cells.
Cell theory states that cell is the basic unit of life, all living organisms are made up of one or more cells and they typically arise from existing cells i.e pre-existing cells give rise to new ones through the process of cell division.
From the image of the salamander's skin cell, we can see that it comprises of many cells and are these look very much alike, meaning they are from pre-existing cells.