This is the Conservation of energy. We say energy is conserved because none is lost in the process.
Answer:
Charge on B is 12 uC.
Explanation:
Initial charge on A = 32 uC
Initial charge on B and C = 0
Now A touches to B, so the charge on A and B both is
q = (32 + 0) / 2 = 16 uC
Now A touches to C, so the charge on A and C both is
q' = (16 + 0) / 2 = 8 uC
Now again A touches to B so the charge on B is
q''= (8 + 16) / 2 = 12 uC
neutral objects is correct