Vemuri's Brain Teaser-4

[Ravisankar Vemuri]

In a country there are exactly twenty cities, and there is exactly one
direct road between any two cities. No two direct roads have an
overlapping road segment. After the election dates are announced,
candidates from their respective cities start visiting the other
cities. Following are the rules that the election commission has laid
down for the candidates:
• Each candidate must visit each of the other cities exactly once
• Each candidate must use only the direct roots between two cities for
going from one city to another
• The candidate must return to his own city at the end of the
campaign
• No direct road between two cities would be used by more than one
candidate
The maximum possible number of candidates is:
(A)5 (B)6 (C)7 (D)8 (E)9