The catalyst used in the water-gas shift reaction is

Explanation

**Step-by-Step Text Solution:**

1. **Understanding the Water-Gas Shift Reaction:**
- The water-gas shift reaction is an important chemical process that involves the conversion of carbon monoxide (CO) and steam (H2O) into carbon dioxide (CO2) and hydrogen gas (H2).
- The reaction can be represented as:
\[ \text{CO} + \text{H}_2\text{O} \rightleftharpoons \text{CO}_2 + \text{H}_2 \]
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