Which characteristic makes us a membrane selectively premeable

- helps us stay on the ground (without gravity we would float and float into space and inevitably die)

- helps us hold things in our hands (even if we let go the objects won't go flying)

- makes it easy for us to do daily things

- lets us understand why things happen and why objects fall to the ground

- suns gravity helps keep the earth the great amount of distance away from the sun so we can get the exact amount of sunshine