The microphone on a Cisco TelePresence System 3000 is switching incorrectly to a camera that does not have an active speaker. What is the first step that an engineer should take to troubleshoot this issue?

A.	Check whether the microphone is properly plugged in.
B.	Run the microphone calibration procedure.
C.	Plug all microphones into the primary codec.
D.	Check whether the cable from the microphone is plugged into the correct receptor on the codec.