Volume is the amount of space an object takes up
Homogeneous:
denoting a process involving substances in the same phase (solid, liquid, or gaseous).
Herogeneous:
of or denoting a process involving substances in different phases (solid, liquid, or gaseous).
Answer:
electrons should be added to one of these spheres to make it electrically neutral.
Explanation:
Total charge on each sphere = +3.0 μC =

In order to neutralize the positive charge equal magnitude of negative charge is to be added.
Total charge electrons, Q= -3.0 μC =
Number of electrons = n
Charge on a single electron, e = 
Q = n × e


electrons should be added to one of these spheres to make it electrically neutral.