Option B (inventory turnover) is correct because according to the textbook, Activity Ratios measure the speed at which business activities are performed. Inventory Turnover Ratio is specifically listed under Activity Ratios and 'determines the number of times inventory is converted into revenue from operations during the accounting period.' It expresses the relationship between cost of revenue from operations and average inventory, thereby measuring the activity of a firm's inventory. Options A, C, and D are incorrect because average collection period relates to receivables, while liquid ratio and current ratio are liquidity measures, not activity ratios.