Introduction:
At low temperatures, the most suitable type of thermometer to use is an alcohol thermometer. This is because alcohol has a lower freezing point compared to water and mercury. In this response, we will explore the reasons behind this choice and discuss the properties of different types of thermometers.

Properties of Different Types of Thermometers:
1. Water Thermometer:
- Water freezes at 0 degrees Celsius and boils at 100 degrees Celsius.
- Because of its freezing point, water is not suitable for measuring temperatures below 0 degrees Celsius. It would freeze and expand, potentially damaging the thermometer.

2. Alcohol Thermometer:
- Alcohol, specifically ethyl alcohol or ethanol, has a freezing point of -114 degrees Celsius and a boiling point of 78 degrees Celsius.
- This wide range of temperature measurement makes alcohol thermometers suitable for both low and high temperatures.
- Alcohol also has a lower specific heat capacity compared to water, meaning it heats up and cools down faster, allowing for quicker temperature readings.

3. Mercury Thermometer:
- Mercury has a freezing point of -38.83 degrees Celsius and a boiling point of 356.73 degrees Celsius.
- While mercury thermometers can measure low temperatures, they are not suitable for extremely low temperatures due to their higher freezing point compared to alcohol.

4. Clinical Thermometer:
- A clinical thermometer is specifically designed to measure human body temperature.
- It contains a special liquid, typically a mixture of toluene and ethanol, which has a lower freezing point and a narrower range of temperature measurement suitable for human body temperature.

Conclusion:
In conclusion, at low temperatures, an alcohol thermometer is the most suitable choice due to its lower freezing point compared to water and mercury. Alcohol thermometers can measure a wide range of temperatures, including those below the freezing point of water. They are also faster in terms of heating up and cooling down, making them efficient for temperature measurements. Other types of thermometers, such as water, mercury, and clinical thermometers, have specific applications and limitations that make them less suitable for low-temperature measurements.

So the answer is alcohol thermometer as it has low temperature and is suitable for that type of temparature