Give the appropriate term defined by the statements given below :
The substance that releases hydronium ion as the only positive ion when dissolved in water.

Explanation

To solve the question, we need to identify the term that corresponds to the definition provided: "The substance that releases hydronium ion as the only positive ion when dissolved in water."

### Step-by-Step Solution:

1. **Understanding Hydronium Ion**:
- The hydronium ion (H₃O⁺) is formed when an acid donates a proton (H⁺) to a water molecule. This means that in aqueous solutions, H⁺ ions do not exist freely; they associate with water to form H₃O⁺.

**Hint**: Remember that H⁺ ions in water are not found alone; they combine with water to form hydronium ions.
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