Both systems
prevent excessive rudder deflection at high speed.
By changing the ratio, even a full movement of the pedals will not give full
deflection of the rudder. So the rudder movement is limited, but not the
pedals. (i.e. not both, so I is wrong)
A variable stop system progressively limits deflection of the rudder as speed
is increased, but by physically constraining it, NOT by changing the ratio. But
within the range of motion that it has, the same relationship between pedal
deflection and rudder deflection exists. (the ratio
does not change, so II is wrong)