The answer would be point A.
Hope this helped you.
Explanation:
In the given situation two forces are working. These are:
1) Electric force (acting in the downward direction) = qE
2) weight (acting in the downward direction) = mg
Therefore, work done by all the forces = change in kinetic energy
Hence,
It is known that the weight of electron is far less compared to electric force. Therefore, we can neglect the weight and the above equation will be as follows.
v =
= 592999 m/s
Since, the electron is travelling downwards it means that it looses the potential energy.
It has to be the last one because whenever lights are turned on it decreases because all lights are on at the same time. It's good to just have one light on. It doesn't use as much electricity.