单项选择题
A．was playing a joke. B．was leaving Boston. C．was moving to Boston. D．was selling his house himself.
A．air traffic problems. B．safety improvement. C．the number of flights. D．flight training courses.
A．To control patrol boats on the River Danube. B．To end economic sanctions against Serbia. C．To step up economic sanctions against Serbia. D．To send police officers to search the river.