Two liquid-in-glass thermometers in a liquid that is well mixed are each separately read by $10$ different students. Every student records that one thermometer shows $21\,^{\circ}\text{C}$ and the other shows $23\,^{\circ}\text{C}$. What might account for the discrepancy?
- AThe liquid is not all at the same temperature.
- BThe readings are not precise.
- CThere is a random error affecting the readings.
- DThere is a systematic error affecting the readings.