As it was almost time for the flight, all the passengers got ______ the plane.
Huge trees on the green land were cut down, ____ the city being buried by sand.
Loulan is believed ____ by sandstorms from AD 200 to AD 400.
In 89 BC, Pompeii became a rich and busy city and near the city ____ a volcano.
While the soldier’s idea was interesting, the system was too difficult to be ____.
In old days, books for blind people used paper ____ against metal wire to form letters.