I believe that would be irritability.
Multicellular organisms can be much larger and more complex. This is because the cells of the organism have specialised into many different types of cells such as nerve cells, blood cells, muscle cells all performing different functions.
Answer:
Carbon dioxide (CO2) and water (H2O)
I think the correct answer from the choices listed above is option A. Cells divide in order to maintain a surface area large enough to support their cytoplasm. When they divide, their volume decreases which enables them to obtain enough nutrient and expel wastes.