The correct answer is C. Asset turnover will decrease and net income margin will increase.
Asset turnover is calculated by dividing total revenue by average assets. By impairing the generation facility, the total assets of Energy Corp. will decrease, which will result in a decrease in the denominator of the asset turnover ratio. Therefore, the asset turnover will decrease.
Operating profit margin is calculated by dividing operating profit by total revenue. As the generation facility was fully impaired, it will no longer generate any operating profit, which will reduce the numerator of the operating profit margin ratio. Therefore, the operating profit margin will increase.