The soldiers have to stand for hours without changing _______.

Most people are in favor of the _______ against smoking in public places.

There were so many cars held up by the heavy rain on the road that we had no        but to wait.

At the __________ of the gun,the runners dashed from their starting points.

As the quality of the city’s air continues to give rise to ______, the residents are encouraged to set off fewer fireworks.