Which of the following is an example of a material accounting change that requires recognition and an unmodified opinion on the entities financial statements?
a. a change in the estimate of useful lives used to depreciate property plant and equipment
b. a change in the entities form of reporting entity
c. management has changed from one generally accepted accounting principles to another but has not provided reasonable justification
d. a change from an accounting principle that conforms with GAAP to one that does not