The LED on a MacBook (13-inch Late 2009) MagSafe power adapter does not illuminate at all when it is plugged into the MacBook and you know the adapter is
connected to a known good power source. What is the most likely cause of this symptom?

A.
The MacBook has a faulty backup battery.

B.
The MagSafe adapter needs to be reset first.

C.
The MacBook has a faulty magnetic sleep sensor.

D.
A MagSafe adapter connector pin is stuck down or dirty.