Which of the Following Explanations Most Likely Would Satisfy an Auditor

Which of the following explanations most likely would satisfy an auditor who questions management about significant debits to the accumulated depreciation accounts?

A) The estimated remaining useful lives of plant assets were revised upward.
B) Plant assets were retired during the year.
C) The prior year's depreciation expense was erroneously understated.
D) Overhead allocations were revised at year-end.