题目内容：

语法填空

If you have ever watched a movie that featured old Beijing，there is a good 1.(possible)that it contained a scene with a flock of pigeons flying over quadrangular dwellings (Siheyuan)，2.( give) off a uniquely harmonic(和声的)buzzing sound as they flew by．That sound is 3. local residents remember when they think of old Beijing．Every city has 4.( it)unique sights and sounds， and the "sound of old Beijing" is the pigeon whistle．

Pigeon whistles (also called pigeon bells) are whistles that 5.( tie) on the tails of pigeons so that when they fly， the air that flows through the whistle creates a harmonic sound．Over 6. last several centuries， Beijing residents have liked to raise pigeons and let them soar through the sky every day． Regardless 7. whether it is a windy morning in spring 8. a cloudless day in late autumn， people can always see a flock of pigeons flying around in the sky and hear the beautiful sound they make while flying． Up until the 1950s， pigeon markets in Beijing were very 9.(promise)．

But with the passing of time and advancement of urban development， fewer and fewer people in Beijing are raising pigeons．10.( consequent)， the sight of pigeons flying around with their accompanying harmonic sound is becoming increasingly rare．