What performs extremely complex functions in the body?

The correct choice highlights that organs perform extremely complex functions within the body. Each organ is specialized to carry out specific tasks that are essential for maintaining health and supporting life. For example, the heart pumps blood throughout the body, the lungs facilitate gas exchange, and the liver processes nutrients and detoxifies substances. These functions are intricate and involve numerous biochemical processes and interactions with other organs and systems.

While cells and tissues are fundamental components of biological organization, they perform more localized and less complex functions compared to organs. Cells are the basic units of life, and while they carry out necessary functions like metabolism and energy production, they do not perform the high-level coordinated activities that organs do. Tissues, made up of groups of similar cells, serve supportive roles and can perform specific functions, but they too lack the complexity and coordination found at the organ level.

Systems are made up of multiple organs that work together to perform broader functions, which adds another layer of complexity. However, when it comes to performing extremely complex functions, individual organs stand out as the primary units that achieve this through their specialized roles and interdependence within systems. Thus, organs are recognized for their intricate and essential functions in the human body.