Answer:
Follows are the solution to the given question:
Explanation:
For point a:

For Point b:


For Point C:
For point D:

The electrostatic potential energy, U, of one point charge q at position d in the presence of an electric field E is defined as the negative of the work W done by the electrostatic force to bring it from the reference position d to that position

Thus, to double the electric potential energy U we need to reduce the distance of separation by half (1/2) because they are inversely proportion
The answer is B.
Temperature is just another term for the average kinetic energy of a substance.
There is a threshold frequency for each metal, and only light of a frequency higher than this threshold causes electrons to be emitted from the metal surface.