What is the reason for this?

An engineer has been noticing the power settings on several of the office APs change from day to day ever since two more APs were installed. After logging into the WLC, the engineer verifies that the power levels on 4 of the 802.11n radios are fluctuating up and down.

What is the reason for this?
A . The controller has the APs in H-REAP mode and are on a Layer 2 connection instead of Layer 3.
B . The RRM has revealed a bad survey and is attempting to power down some of the radios to make up for it.
C . The WLC has created temporary coverage holes while stepping through power levels for some of the APs.
D . Several APs have high levels of overlapping coverage in the same area and the WLC is using RRM to correct the cell sizes AP coverage.

Answer: D