...................... is a good conductor of heat and electricity and used to make electrodes.

Answer

**Step-by-Step Solution:**

1. **Identify the Properties Required:**
The question asks for a substance that is a good conductor of heat and electricity and is used to make electrodes.

2. **Consider Common Conductors:**
Common materials that are known to be good conductors of heat and electricity include metals like copper and aluminum, but the question specifies a material used for electrodes.

3. **Recall Carbon Allotropes:**
Among carbon allotropes, we need to identify which one is a good conductor. The two main allotropes of carbon are graphite and diamond.

4. **Evaluate Graphite:**
Graphite is known to be a good conductor of both heat and electricity due to its structure. It has delocalized electrons that allow it to conduct electricity efficiently.

5. **Confirm Usage in Electrodes:**
Graphite is widely used to make electrodes in various applications, including batteries and electrolysis, due to its conductivity and stability.

6. **Conclude the Answer:**
Therefore, the substance that fits the description of being a good conductor of heat and electricity and is used to make electrodes is **graphite**.

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