Answer:
RBC-biconcave
Skin-polygonal(might be best answer as shape changes according to the layer)
nerve cells-dendritic or tree shape(star shape with tail)
rbc cells have biconcave shape to allow increased surface area for exchange of gases and passage through narrow capillaries.
skin cells have mainly barrier function and polygonal shape allows them to extensively arrange themselves to make an efficient barrier.
nerve cells-they have to gather impulses from various other cells in many directions so star shape cell body allows this and tail(axon) is for transmitting it which in turn relays this information to other nerve cells this completing the pathway for sensory impulses and motor responses.
Step-by-step explanation: