A correct electrochemical series can be obtained from K,Na,Ca, Al, Mg, Zn, Fe, Pb, H,Cu, Hg, Au, by interchanging

Options

A. Al and Mg
B. Zn and Fe
C. Zn and Pb
D. Pb and H

Explanation

To arrange the metals K, Na, Ca, Al, Mg, Zn, Fe, Pb, H, Cu, Hg, Au in the correct electrochemical series, we need to follow the order of their reactivity. The electrochemical series ranks metals based on their ability to displace other metals from solutions of their ions, which is a reflection of their reactivity.

### Step-by-Step Solution:

1. **Identify the Most Reactive Metal**:
- Potassium (K) is the most reactive metal among the given options.

2. **List the Metals in Order of Reactivity**:
- The order of reactivity for the metals provided is:
- K > Na > Ca > Mg > Al > Zn > Fe > Pb > H > Cu > Hg > Au

3. **Check the Given Order**:
- The initial order provided is K, Na, Ca, Al, Mg, Zn, Fe, Pb, H, Cu, Hg, Au.
- In this order, Al and Mg are incorrectly placed.

4. **Interchange Al and Mg**:
- The correct order should have Mg before Al. Therefore, we interchange Al and Mg.

5. **Final Correct Order**:
- The final correct electrochemical series is:
- K > Na > Ca > Mg > Al > Zn > Fe > Pb > H > Cu > Hg > Au

### Summary of Changes:
- The only change needed to obtain the correct electrochemical series is to interchange Aluminum (Al) and Magnesium (Mg).