Answer:
B
Step-by-step explanation:
Neither is necessarily correct.
A potentiometer is a 3-terminal device whose resistance at the "tap" terminal will vary from the whole amount of the resistance between the other two terminals to none of it. The device can be hooked up as a voltage divider. When the device is of such a construction that the resistance is varied by turning a shaft, it can be mechanically connected so that it will detect movement.
Some potentiometers are controlled by a digital command, so have no mechanical connection. Of course, there is no requirement they be connected as a voltage divider.
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A magnetoresistive sensor, by definition, is one that changes resistance when the magnetic field it is exposed to changes. If it is connected to a (more or less) constant voltage source, the current through the sensor will change when it is influenced by a magnetic field. (Technician B is correct in this regard.)
However, the sensor may be connected to a constant-current circuit, so that the current does not change with magnetic field. In that case, the voltage will change, not the current.
Technician B is more likely to be correct.