b)It doesn't have a Hamilton circuit . Because :
A Hamilton circuit is the longest circuit .
It never contains other circuits. (1)
It always contains every edges next points x that d(x) = 2 . (2)
If having a Hamilton circuit ,the Hamilton will contains eg , gc , cd and ed (2) . But these 4 edges create a circuit . Arcording to (1) , there is a conflict .
So , the graph has no a Hamilton circuit .