The boy's bad behavior ____ his mother lots of sleepless nights.
Although the educational systems have been a lot, the loads of the students are still very heavy.
For sustainable development, the government has decided to give to those energy conserving and environment-friendly business in many aspects.
The present system no longer meets the changing needs of our customers; we have to make a (n) management system.
As a teacher rich in experience, he knows how to his ideas to these new students in a limited period of time.
One of my classmates accidentally he had cheated in the last examination, or he wouldn’t have got so high a mark.