Final answer:
The appropriate time to stop recording depreciation expense on an asset is when its carrying amount exceeds its fair value.
Step-by-step explanation:
The correct answer to this question is b. carrying amount exceeds its fair value. When an asset's carrying amount exceeds its fair value, it indicates that the asset has suffered an impairment loss. In this case, the remaining future economic benefits of the asset are expected to be lower than its carrying amount, and as a result, it is appropriate to stop recording depreciation expense.