Interesting post.
The correct answer, however, would be (d) servo tabs.
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Comxtek wrote >>>AILERON AND AILERON TRIM CONTROL SYSTEM - BALANCE PANEL AND TAB
Purpose
The aileron balance panels and tab decrease the force necessary to move the aileron in flight.<<<
Yes, they do indeed reduce the force required to position the control surface, but they don't actually displace (move) the surface during manual reversion.
Servo tabs or in Boeing speak, control tabs, are dual purpose tabs. In powered operation they reduce the force required to position the control surface. During manual reversion, the control (servo) tab unlocks and is directly controlled by cockpit control inputs to aerodynamically move the control surface.