Answer:
A. Organ
Step-by-step explanation:
- The cell is the fundamental basic unit of life. A cell is made up of organelles which are the smallest biological level of organization in living organisms.
- A group of cells joins together to form a tissue that performs a specific function. Examples of tissues in animals include nervous tissue, connective tissue, muscle tissue, and epithelial tissue.
- A group of two or more tissues combines to form an organ. This means an organ function depends on the tissues making it. Examples of organs are lungs, heart, kidney, etc.
- More than one organ combine to form an organ system such as the respiratory system, urinary system, digestive system, etc.