Final answer:
The mark down rate, when the sale price is 30% less than the retail price, is indeed 30%. This is a direct reduction on the original price, making the sale price 70% of the retail price.
Step-by-step explanation:
The question is asking for the mark down rate if the sale price is 30% less than the retail price. The correct answer is D) 30%. This means that the original price has been reduced by 30%, making the sale price 70% of the original retail price. Any other options (15%, 20%, 25%) would indicate a lower percentage of markdown, which is not the case here according to the given condition that explicitly states a reduction of 30%. Therefore, the markdown rate is exactly 30%, matching the details provided in the student's question. It is important not to confuse the markdown rate with the final sale price or any other discounts that might be applied.