I must confess that in my previous post I made the mistake of answering the question I wanted to be asked rather than the one actually asked by Gin Slinger. A clear failure to RTQ!!
My post was based on the assumption that the controls had jammed, in which case only trim tabs, spoilers or variable incidence tailplanes would do the job.
The question actually asks about the manual reversion condition. This is rarely used in modern aircraft, because they tend to have multiple redundant hydraulic systems.
In those aircraft which employ manual reversion, the use of spring tabs, balance tabs or servo tabs will be capable of providing assistance in this condition. This obviously poses a problem in selecting the best answer to this question.
One problem with balance tabs and servo tabs is that they move in the opposite direction to the main control surfaces, so they reduce the overall effectiveness of the controls. They are therefore unlikely to be used in multiple redundant power operated systems.
A further problem with servo tabs is that control effectiveness is very poor until a reasonably high airspeed has been attained.
The descriptions of the B737 system provided above appears to refer to an internal aerodynamic balance system. This is not one of the options in the original question. If however the B737 actually uses both internal aerodynamic balance and balance tabs to provide manual reversion, then this is probably what the examiners are looking for.
A number of questions in feedback lists appear to indicate that the examinaers look through the manuals of their reference aircraft (B737 and A310) and pick out interesting little curiosities to ask questions about! Another example is "where would you use Krueger flaps"? The answer they want is at the wing roots. But this ignores the fact that some older aircraft still in operation have full span Kruegers.