Final answer:
Tissues are groups of similar cells that work together, which combine to form organs. These organs are part of an organ system and collectively make up an organism, which can be a single cell or a complex multicellular entity. option a is correct.
Step-by-step explanation:
Tissues are groups of cells that have similar structures and functions. In larger organisms, cells combine to form tissues, which in turn collaborate to create organs. Organs are collections of tissues that work together to perform a specific function, and these are not just in animals but also in plants.
These organs are grouped into organ systems, such as the circulatory system which includes the heart and blood vessels and is responsible for transporting blood throughout the body. Lastly, organisms are individual living entities that can be single-celled, like microorganisms, or multicellular, like animals and plants.