Ok, so you have a couple of waypoints, and the great circle
track between them is 100. Meanwhile, your aircraft is currently achieving a
track of 120 degree.
So, tracking error is 20 Right, so that answer is definitely correct.
Why is "Aircraft Diverging" wrong?
If the aircraft is in track, or right of track, then it is diverging. However,
if it's left of track then it is converging. The point being we don't know
where the aircraft is because the question doesn't tell us.
TKE isn't a bad thing if you are regaining track
In a similar manner, if TKE is zero this doesn't mean the aircraft is on track.
It could just as well be paralleling.
I suppose the gotcha in this question is to play on the natural assumption that
you are on track to start with.