Name the following substance :
A strong but non-volatile mineral acid.

Explanation

To solve the question, we need to identify a substance that is described as a strong but non-volatile mineral acid. Here’s a step-by-step breakdown of the solution:

### Step 1: Understand the terms used in the question
- **Strong Acid**: A strong acid is one that completely dissociates in water, releasing a high concentration of hydrogen ions (H⁺).
- **Non-volatile**: Non-volatile substances have a low tendency to vaporize. This means they have a high boiling point and do not easily turn into gas at room temperature.
- **Mineral Acid**: These are inorganic acids, typically derived from minerals, and are strong acids.

### Step 2: Identify common strong mineral acids
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