Final answer:
The false statement is that the operating income of manufacturers will always be the same, regardless of the costing method used.
Step-by-step explanation:
The statement that is false among the options provided is 'c. the operating income of manufacturers will always be the same, regardless of whether variable or absorption costing is used'.
This is because operating income can differ depending on whether a company uses variable costing or absorption costing. This difference arises primarily due to the way inventory costs are treated under each costing method.
Under variable costing, only variable costs are included in the cost of goods sold, and fixed manufacturing overhead costs are treated as period expenses.
Conversely, absorption costing includes both variable and fixed manufacturing overhead costs in the cost of goods sold.
Therefore, changes in inventory levels can affect operating income; if inventory levels increase, more fixed costs are allocated to ending inventory and are not expensed on the income statement, potentially resulting in a higher operating income under absorption costing.
Both contribution margin and the organization of costs by behavior, as mentioned in option a and b, are indeed integral parts of variable costing. Additionally, as stated in option d, under absorption costing, fluctuations in inventory levels will impact operating income.