Explanation:

- We know the cost price is 25% less than the selling price. This means the selling price is higher than the cost price.

- Consider the selling price (SP) as 100 units. The cost price (CP) would then be 75 units (25% less than SP).

- Profit is calculated as Selling Price minus Cost Price, which is $100-75=25$ units.

- To find the profit percentage, use the formula: $(\text{Profit}/\text{Cost Price})\times 100$.

- Here, it becomes: $(25/75)\times 100=33.33\mathrm{\%}$.

- Therefore, it is a profit of 33.33%.

- Option 1: 33.33% loss - Incorrect; this is a profit, not a loss.

- Option 2: 66.67% profit - Incorrect; the percentage is not this high.

- Option 3: 33.33% profit - Correct -

- Option 4: 66.67% loss - Incorrect; actually, there is a profit, not a loss.