4. Which of the following statements is true about depreciation? a. Using the straight-line method of depreciation, equal amounts would be recognized as depreciation expense across the useful life of the asset, unless other estimates change. b. The residual value of a PPE increases the amount to be charges to depreciation. C. Land is always depreciated using the straight-line method. d. The depreciation expense represents the unexpired portion of the cost of a PPE