We have a fixed conductor having a cavity inside. There is a point charge `q_(1)` kept inside the cavity charge appearing at the inner surface of the cavity is `q_(2)`. Charge appearing at outer surface of conductor is `q_(3)` and there lies another point charge `q_(4)` out side the conductor. Whole situation is shown in figure. `q_(4)`. is held stationary by applying an external force `vecF_(0)` on it. Three points A, B and C are shown. Answer the following two questions.
Q. If keeping the magnitude and nature of `q_(1)` fixed position of `q_(1)` is changed inside the cavity. Then choose the correct option(s)

Options

A. External force required to keep `q_(4)` stationary remains unchanged
B. intensity of electric field at point C remains unchanged
C. intensity of electric field at point B remains unchanged
D. intensity of electric filed point B only due to `q_(2)` remains unchanged.

Answer

A, B, C