consider A,B,C....as buildings 1,2,3.... as roads
1) set {1,3,6} it not prefrred set...but it is possible to find prefffred set..for some other graph..(remove D,G building with roads 4,7 then u will find prefffred set {1,3,6} )
2) it is not possible at all...try in graph
so both statements are wrong