Carbon-Carbon double bond rotation
Here you need to consider two factors. 


The one which follows $4n+2$ rule.
The stability of the ring.


When we see the IIIrd one, the structure don't follow the $4n+2$ rule when the double bond breaks. That means, that the double bond will be reluctant towards breaking. Hence its stability will be least.

COMING TO NEXT ONE

The order of stability of the ring is in the order: 6−member > 5−member > 7−member > 4−member > 3−member.

So when we combine these facts we find the correct order is B>A>C.