A. Specialized cells and B. Organ systems are features that are present in multicellular organisms but not in unicellular organisms.
Specialized cells are cells that have developed unique structures and functions to perform specific tasks within the organism. In multicellular organisms, different types of specialized cells come together to form tissues, which in turn form organs and organ systems.
Organ systems are groups of organs that work together to perform specific functions within the organism. For example, the digestive system, respiratory system, and circulatory system are all examples of organ systems that are present in multicellular organisms but not in unicellular organisms.
Cell division (C) and cell organelles (D) are features that are present in both unicellular and multicellular organisms. Cell division is necessary for both types of organisms to reproduce, while cell organelles are structures that are present within cells to perform specific functions.