accounting policies and estimates

Hello,
Could you please explain why the answer to the following question could not be C (correct answer is A).

Which of the following is a change of accounting policy under IAS 8 Accounting Policies, Changes in Accounting Estimates and Errors?

A. Classifying commission earned as revenue in the statement of profit or loss, having previously classified it as other operating income.

B. Switching to purchasing plant using finance leases from a previous policy of purchasing plant for cash.

C. Changing the value of a subsidiary’s inventory in line with the group policy for inventory valuation when preparing the consolidated financial statements.

D. Revising the remaining useful life of a depreciable asset.