depends on the metals you use for making the thermocouple, it most probably depends on the relative conductivities of the metals in question. regarding this question, i think by resistance thermometer they are referring to thermistor, which has a very high sensitivity over a small range, so more accurate calibration is possible in that range, whereas a thermocouple is unlikely to have such a high sensitivity.
[can i ask how you are scoring on average in paper 4 past papers?]