12. prove or disprove: if b is a block of order 3 or more in a connected graph g, then there is a cycle in 14] b that contains all the vertices of b. a graph g is a critical block if g is a block and for every vertex v, the graph g - v is not a block. similarly a graph g is a minimal block if g is a block and for every edge v, the graph g- e is not a block.