Its really a poorly worded question and a true answer cannot be provided. Control effectiveness address whether the control can do what it is designed to do. Stabilizer for stability and elevator to change pitch attitude.
- The question does not address the CG's starting location, and its distance to the center of pressure/lift (only that we know its moving "closer").
- If CG moves aft of CG limits - aircraft is trending toward unstable, and controls are becoming less effective. Less nose down moment, does elevator maintain effectivenss to lower nose? If CG moves aft of CL then lift acts through the CG for a nose up moment (not good)
- If CG moves forward of CG limits, aircraft is trending towards stability to the point that the controls may be ineffective. More nose down moment, does elevator maintain effectivness to raise nose?
- If the aircraft is operated within the its CG limits, control effectiveness will be within design limits.
Are any of the above A, B, C or D?