Concept:Division of labour means different parts of an organism perform specialized functions.
Explanation:It occurs in both unicellular and multicellular organisms.
In unicellular organisms like amoeba, organelles carry out specialized jobs.
In multicellular organisms, cells, tissues, and organs are specialized for different functions.
For example, nerve cells transmit signals and muscle cells help in movement.
This specialization increases efficiency and helps perform complex tasks.
Answer:Option D: both unicellular and multicellular organisms.