AP BIOLOGY

Detailed explanation-1: -Tissue is a group of cells that have similar structure and that function together as a unit. Primary types of body tissues include epithelial, connective, muscular, and nervous tissues. Epithelial tissues form the covering of all body surfaces, line body cavities and hollow organs, and are the major tissue in glands.

Detailed explanation-2: -Tissues are groups of cells that have a similar structure and act together to perform a specific function. Different tissues make up organs.

Detailed explanation-3: -A group of tissues performing a particular function in the body forms an organ. A group of organs that work together to maintain a stable internal environment and perform a particular function is called as organ system. Thus, the correct answer is ‘Organ.