Mercury is used in thermometers because

Options

A. it does not stick to the glass
B. It expands on heating
C. it is a liquid
D. all of these

Explanation

**Step-by-Step Solution:**

1. **Understanding the Properties of Mercury:**
- Mercury is a unique metal that is liquid at room temperature. This property makes it suitable for use in thermometers.

2. **Non-Stick Property:**
- One of the key reasons mercury is used in thermometers is that it does not stick to the glass. This allows for accurate readings as the mercury can move freely within the glass tube without clinging to the sides.

3. **Expansion on Heating:**
- Mercury expands when heated. This property is crucial because as the temperature rises, the mercury expands and rises in the glass tube, allowing for a clear measurement of temperature.

4. **Liquid State:**
- Mercury remains in a liquid state at room temperature due to its low melting point of -38.83 degrees Celsius. This characteristic is essential for the functionality of thermometers, as it ensures that the mercury is always in a liquid form for temperature measurement.

5. **Conclusion:**
- Given all these properties—non-stick to glass, expansion on heating, and being a liquid—mercury is an ideal substance for use in thermometers. Therefore, the correct answer to the question is option D: All of these.

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