I am just going to give a hint so that your teacher's "think" will serve it's purpose. In the first case, make each member of parliament as a node and then draw edges between him and opposition members. It will be a n-regular graph depending on the number of oppositions which in this is case is 3. Then keep removing edges such that one member has only one edge. Draw a simple 3-regular graph and remove edges and see how this will turn out to be.