Final answer:
The term that best describes epithelial cells in the skin working together to perform a specific function is Tissue. Therefore, the correct option is 4.
Step-by-step explanation:
In biological organization, tissues are groups of cells that work collectively to carry out a particular function. Epithelial tissue, in the context of the skin, forms a protective layer, serving as a barrier against external factors and helping with absorption and secretion.
While an atom (1) is the basic unit of matter and a molecule (2) is a combination of atoms, these terms do not encompass the organized structure of cells working together. An organ (3) is a higher level of organization composed of different tissues, but in this case, the specific focus is on the coordinated function of epithelial cells, which is described as tissue.
Therefore, the correct option is 4.