Complete the following by selecting the correct option from the choices given :
The metal which does not react with water or dilute `H_2SO_4` but reacts with concentrated `H_2SO_4` is ________ .(`Al//Cu//Zn//Fe`)

Explanation

To solve the question, we need to identify the metal from the given options that does not react with water or dilute sulfuric acid but does react with concentrated sulfuric acid. The options provided are: Al (Aluminum), Cu (Copper), Zn (Zinc), and Fe (Iron).

### Step-by-Step Solution:

1. **Understanding Reactivity with Water and Dilute Acid**:
- Metals that do not react with water or dilute acids are generally those that are lower in the reactivity series than hydrogen.
- **Copper (Cu)** is known to be less reactive than hydrogen, meaning it will not displace hydrogen from dilute acids or react with water.

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