While __________ for the bus, I happened to come across my childhood friend, Tom.
____ since the night before, I felt very hungry.
_____ with the accident, he was forced to resign.
They use computers to keep the traffic smoothly.
All flights ________called off because of the terrible weather, they had to go there by train.
After the six-party talk in Beijing, an agreement was reached _________ that North Korea would abandon _________ nuclear weapons.