For which of the following events would an auditor of a nonissuer most likely issue an unmodified report with an emphasis-of-matter paragraph referencing a lack of consistency?

a. A change in useful life used to calculate the provision for depreciation expense. The effect of the change is material.

b. A change in reporting entity as a result of purchasing a subsidiary during the year. The effect of the change is material.

c. A change from percentage of completion to completed contract method. The effect of the change is not material.

d. A change in depreciation method from straight-line to double-declining balance. The effect of the change is material.