Explanation:

To solve this, let's break it down step by step:

- Original Cost Price: Let's assume the cost price of the mustard oil is ?100.

- Marked Price: Since the marked price is 25% more than the cost price, it becomes ?125.

- Selling Price: For no profit, no loss, the selling price should match the original cost price, which is ?100.

- Percentage Reduction Needed:

- The required reduction from the marked price is ?125 - ?100 = ?25.

- Calculate the percentage reduction: $(?25/?125)\times 100=20$.

So, the mustard oil should be sold at 20% less than the marked price to have no profit and no loss.

- Option 1: 15% - This would still keep the selling price above the cost price.

- Option 2: 20% - This rightly brings the selling price to the cost price.

- Option 3: 18% - This results in selling above the cost price.

- Option 4: 22% - The price would go below the cost price, resulting in a loss.

Option 2: 20%