Final answer:
A student should report their temperature measurement to one decimal place when using a mercury thermometer with 0.1ºC graduations.
Step-by-step explanation:
A student using a mercury thermometer with 0.1ºC divisions should report their temperature measurement to one decimal place. This is because the thermometer's graduations are to the nearest tenth of a degree, and the convention for reporting measurements is to go one decimal place beyond the smallest division. Therefore, option (b) 1 decimal place is the correct choice.
In physics, it's important to report measurements to the correct degree of precision. Over-reporting precision can suggest a false degree of accuracy, so the standard practice is to report one more decimal place than the measurement device can directly measure. Since the thermometer measures to the nearest 0.1ºC, the student should record their measurement to the nearest 0.1ºC, which is one decimal place of precision.