2. What kind of graph (from Table 1) can be used to model a highway
system between major cities where
a) there is an edge between the vertices representing cities if there is
an interstate highway between them?
b) there is an edge between the vertices representing cities for each
interstate highway between them?
c) there is an edge between the vertices representing cities for each
interstate highway between them, and there is a loop at the vertex
representing a city if there is an interstate highway that circles this
city?