Which of the Following Would Be Treated as a Prior

Which of the following would be treated as a prior period adjustment by Gold Corporation in 2018?

A) In 2018,it was discovered that Gold Corporation recorded the purchase of a warehouse in 2015 as a debit to Repairs Expense.
B) In 2018,Gold Corporation switched from the straight-line method of depreciation to another method of computing depreciation.
C) In 2018,Gold Corporation's management decided that the estimated useful life of its computer equipment should be changed from five years to nine years.
D) In 2018,Gold Corporation sold a segment of the business that it has operated since 2009.