The fact that nearly all galaxies are moving away from us, with more distant ones moving faster, us to conclude thata)the universe is expanding. b)galaxies repel each other like magnets. c)our galaxy lies near the center of the universe.

a) The universe is expanding

Explanation:

All the elements in the universe are still moving at high speeds as result of Big Bang. In fact, all galaxies were accelerated by this event which means their speeds increase constantly. When we study the speed of a galaxy which is close to us, we can record the speed on that moment and check again years later and see the increment of speed as that galaxy is always getting faster and faster and it will be way faster as it get further than us because it will have had more years to build up more speed. Many observations has been done by astronomers and their conclusions about it can be studied on Hubble's Law.  

when it gains or loses electrons

d) physical means can be used to separate the components of air.