It has been proved that taking exercise ________ does good to one’s health. 

“If you’re walking down the right path and you’re willing to keep walking,_____ you’ll make progress”, said the president Obama.

Private cars really provide much convenience to people, and ___ they cause too many problems.

33. The employees have not been paid _______ since the new manager took over this company last month.

The U.S. official said North Korea --- and Iran --- should follow in the steps of Libya, which last December said it would work__________ to allow international weapons inspectors to do their work.