3. explain why multicellularity of an organism requires cell-to-cell communication. let it be a good answer! , means a lot!

I responed to ur other question here u go 
Cell to cell Communication is necessary for cells to carry out various functions. For example nerve cells activate adjacent nerve cells via the synapse using for example acetylchloine and serotonin. Cell to cell signals encourage other cells to divide and act as a dynamic part of a tissue such as epithelia an example of such a signal is epidermal growth factor (EGF). Cells which have a defective epidermal growth factor receptor (EGFR) can form cancerous tumors. Other signals prevent cells from dividing too much. 
Without cell to cell communication cells would divide in a disorganized way. Cancer would occur easily. The nervous system would not function as it relies on cell to cell communication.