Answer:
Energy is stored in the bonds between atoms
Let the sphere is having charge Q and radius R
Now if the proton is released from rest
By energy conservation we can say
now take square root of both sides
so the proton will move by above speed and
here Q = charge on the sphere
R = radius of sphere
The answer is A because An Indicator" changes color when it comes in contact with an acid or a base
An indicator could be anything like:
1) Litmus paper
2) Bromothymol blue
3) Phenolphthalein
D, it is considered unethical today