He __________ his aunt’s when he went to Wuhan on business.
I hope you will study hard and master as much knowledge as possible; otherwise you will have to live a hard life_______.
People are very _____ about the problems ____ the environment.
The headmaster decided to have a word with whoever is ______ this matter.
This injury could mean him ______ tomorrow’s 110-meter hurdles.
_____ twice a year, whether it is a car or a bus, is a rule that every driver must obey in this city.