When depreciation is computed for partial periods under a decreasing charge depreciation method, it is necessary to a. charge a full year's depreciation to the year of acquisition. b. determine depreciation expense for the full year and then prorate the expense between the two periods involved. c. use the straight-line method for the year in which the asset is sold or otherwise disposed of. d. use a salvage value equal to the first year's partial depreciation charge. use the partial year depreciation rule.