can you please solve this with an explanation

5) Which of the following is not a proper adjustment to the basis of property, once the original basis is determined? A. Add repairs and maintenance expenditures exceeding 15% of the cost of the asset within a single year. B. Subtract other capital recoveries such as deductible casualty losses. C. Add improvements and betterment. D. Subtract depreciation allowed or, if no depreciation was claimed, the depreciation that was allowable