Experts are trying to work out a plan to deal with the problems caused by global warming _________ it is too late.

Scientists study ___________ human brains work to make computer.

The old lady had two clever sons, ____ did a good job in the 2010 National College Entrance Exam, though. 

I have been in low spirits ______she left our school

---Could we finish the project according to the schedule?---I doubt that. The problem remains ______ we can get financial aid within this week.