Amedium of free floating positive and negative charges are called ?

Plasma

Explanation:

Mostly this occurs at very high temperatures that cause atoms to lose electrons. Plasma is therefore a gas but of ions. Plasma can conduct electricity and can be influenced by magnetic fields. Plasma occurs mostly in stars where it is the dominant state of matter.  

i think it's c. i'm not sure but i think so.

there is none because earth is stationary and flat.