Final answer:
The basic body plan is organized at the organ level, where different tissues come together to form functional organs within the body.
Step-by-step explanation:
The basic body plan is organized at the organ level. The structure of the human body can be broken down into several levels of organization that increase in complexity. Starting at the smallest, we have molecules that combine to form cells. Cells then combine to form tissues, which are groups of similar cells carrying out specific functions. Different tissues come together to form organs, like the heart or liver. These organs are then arranged into organ systems, such as the skeletal and muscular systems, which work together to carry out complex functions. Finally, organ systems make up the entire organism, which is a living being, such as a human. Following these levels of organization, the answer to the question at hand is (B) Organ level.