Which of the following describes a multicellular organism?

A multicellular organism is defined as an organism that is composed of many cells. These cells work together to form tissues and organs, which then function collaboratively to sustain the organism. Multicellular organisms can vary significantly in complexity, from simple structures like sponges to highly complex organisms like humans.

The key characteristic of multicellular organisms is the specialization of cells, meaning that different types of cells may perform specific functions (for example, muscle cells for movement, nerve cells for signaling, etc.), which is essential for the organisms' overall functionality and adaptability. This contrasts with unicellular organisms, which consist of a single cell that must carry out all necessary life functions independently.

While some organisms—such as plants—can perform photosynthesis (a process that allows them to convert sunlight into energy), not all multicellular organisms have this capability. Additionally, organisms that have no cellular structure, such as viruses, do not fit into the multicellular category as they are not composed of cells in the traditional biological sense. Thus, the essence of multicellular life rests on the presence of multiple cells working in coordination.