Consider the following comments about absorption- and variable-costing income statements:

I. A variable-costing income statement discloses a firm's contribution margin.

II. Cost of goods sold on an absorption-costing income statement includes fixed costs.

III. The amount of variable selling and administrative cost is the same on absorption- and variable-costing income statements.

Which of the above statements is (are) true?

I only.

II only.

I and II.

II and III.

I, II, and III.