82 : Though we have paths from every bridge to every other bridge so technically all the dfs path will result from all options given in the question . But on carefully reading the question it says that you need shortest path from source Root to any other bridge .Therefor option A looks most suitable .
83 . Option A
Following the above connectivity we notice that :
H1,H2 are reachable to from B3 via the port 3 because B3 is connected to B1 and which in turn is connected to the H1,H2.
H9,H10 are also reachable from B3 via B2 from port 1 of B3 .
H5,H6 are reachable from B3 directly via port 1.
H7,H8 via port 2.
H11,H12 via port 2 only because of B3 connection to B2.
H3 and H4 are also reachable directly via port 3 of B3.
Hence answer ( option A.)