An external force (in addition to the spring force) is continually applied to an object of mass

Question:

An external force (in addition to the spring force) is continually applied to an object of mass m attached to a spring that has a spring constant k. The frequency of this external force is such that resonance occurs. Then the frequency of this external force is doubled, and the force is applied to one of the spring systems shown in the drawing. With which system would resonance occur?
(a) A
(b) B
(c) C
(d) D
(e) E