At night, plants _________carbon dioxide and at the same time _________oxygen. So, we may put some in our bedrooms to purify the air.
---When shall we start the reconstruction of the historic building? --- Not until our program ______ by the authority.
I have to reschedule the appointment with you since there is a ______ in my arrangement.
You will have to stay at home all day ______ you finish all your homework.
He works very hard in order to get himself ______ into a key university.
--- Could we accomplish the task according to the schedule? --- I doubt that. The problem remains ______ we can get financial aid within this week.