Choice "A" is correct. A debit to accumulated depreciation decreases the balance in that account. The retirement of plant assets necessitates the removal (decrease) of accumulated depreciation related to the retired asset by debiting accumulated depreciation.
Choice "b" is incorrect. Remember that correction of an estimate is given prospective, not retroactive, treatment. Therefore, there would not be any decrease in the accumulated depreciation taken in previous years, although future credits would be lower than previous credits had been.
Choice "d" is incorrect. If the prior year's depreciation expense were understated (i.e., too low), the entry to correct the error would be a credit to accumulated depreciation.
Choice "c" is incorrect. Revision of overhead allocations would not result in a debit to accumulated depreciation.