<span>In the sentence "Biologists recognize the following levels of cell organization: _____, the choice that correctly completes the sentence is b. cellular, tissue, organ, system, and organism. A cell is the basic unit of living organisms. The group of similar cells that work together to perform a specific job is a tissue. The group of multiple tissues joined together in the functional structure is an organ. Functionally related organs form organ systems, which all together form one organism.</span>
