Unicellular and multicellular organisms both share the feature that the cells reproduce independently.
In unicellular organisms, the entire organism is a single cell that carries out all life functions and reproduces on its own. In multicellular organisms, while cells are specialized for different functions, they can still reproduce independently under certain conditions (like in the case of certain types of tissue or stem cells, for instance). However, the key commonality is that all living cells, regardless of being unicellular or part of a multicellular organism, are capable of reproduction.
The other options provided highlight differences: multicellular organisms have specialized cells, and not all cells must digest food for energy independently.