A Charge 2Q Is Located at the Origin While a Second

A charge 2Q is located at the origin while a second charge -Q is located at x = a. Where should a third charge be placed so that the net force on the charge is zero?

A) x < 0
B) 0 < x < a
C) x > a
D) x < 0 or 0 < x < a
E) 0 < x < a or x > a