Explanation:

• A. Net profit margin is correct because an impairment charge reduces net income (due to the loss recognized) while leaving revenue unchanged. Since net profit margin is calculated as Net Income / Revenue, the ratio decreases.

• B. Debt-to-equity ratio is incorrect because while the impairment charge reduces equity (through retained earnings), it does not affect total debt. This results in an increase, not a decrease, in the debt-to-equity ratio.

• C. Working capital turnover is incorrect because the impairment charge is a non-cash item and does not affect working capital (current assets minus current liabilities) or revenue, leaving the ratio unchanged.

Key Concept: Impairment charges impact profitability ratios by reducing net income but do not typically affect liquidity or leverage ratios unless they involve cash flows or changes in debt/equity structure.