The correct answer is D. both (a) and (b).
If a piece of data is stored in two places in the database, then storage space is wasted because the same data is being stored twice. Additionally, changing the data in one spot will cause data inconsistency because the data in the other spot will not be updated. This can lead to problems if the data is used by other parts of the system.
Option A is correct because storing the same data twice wastes storage space. Option B is correct because changing the data in one spot will cause data inconsistency. Option C is not correct because storing the data in two places does not necessarily make it more easily accessed. Option E is not correct because both options A and B are correct.