Write the name of the electrolyte used in fuel cell.

Explanation

**Step-by-Step Solution:**

1. **Understanding Fuel Cells**: A fuel cell is an electrochemical cell that converts the chemical energy of a fuel (often hydrogen) and an oxidant (often oxygen) into electricity through a reaction.

2. **Identifying the Electrolyte**: In a fuel cell, the electrolyte is a substance that allows ions to move between the anode and cathode while preventing the passage of electrons. This is crucial for the functioning of the fuel cell.

3. **Common Electrolytes in Fuel Cells**: There are various types of fuel cells, and they can use different electrolytes. However, one of the most commonly used electrolytes in alkaline fuel cells is concentrated aqueous potassium hydroxide (KOH).

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