Imagine that an imaginary country has A villages linked by tracks, where a track can be traversed in either direction. For any pair of villages, there is only a set of tracks linking the two villages. Suppose there exists at least one village such that there existdN tracks through which you can enter or exit the village. 

Prove that there are at least d villages such there that there exists only one track via which you can enter or exit the village.

 

There is no reference given. You can solve this using graph theory!