Explanation:

- Let's say the cost price of the article is $C$.

- It is sold at a loss of 40%. So, the selling price is $60\mathrm{\%}$ of $C$, or $0.6C$.

- The nominal amount of loss is $C-0.6C=0.4C$.

- We want to find what percentage this loss $0.4C$ is of the selling price $0.6C$.

- This is calculated as $\frac{0.4C}{0.6C}\times 100\mathrm{\%}$.

- Simplifying, we get $\frac{2}{3}\times 100\mathrm{\%}=66.67\mathrm{\%}$.

- Option 1: 66.67% is the correct answer.