You are moving a negative charge `q lt 0` at a small constant speed away from a uniformly charged non-conducting spherical shell on which resides a negative charge `Q lt 0`. The electrostatic, field of `Q` is `E`. Let `U` be the total energy of the system, `W_(a)` the work done by the force `F_(a)` you exert on `q, W_(E)` the work done by the electrostaitc force `F_(E)` on `q`. Then, as `q` is being moved :
A. `W_(a) = - W_(E)`, therefore `U` remains constant
B. `F_(a) = - F_(E)`
C. `U` increases
D. `U` decreases