What materials were not used for road surfaces during the last century

A．people now know the number of chimpanzees is much smaller than expected
B．it may make it possible for scientists to discover new ways of treating AIDS
C．it proves some deadly human diseases can also be transmitted to wild animals
D．it Will soon help the scientists develop a vaccine that prevents the AIDS virus

A．travel guide
B．language professor
C．school supervisor
D．talkshow host