Mr. Green drove slowly on the way home until he reached the high way, ______ the speed limit was 60 miles per hour.

_________that developed countries want to limit the development of the developing countries in the climate conference in Copenhagen

We can never expect ________ bluer sky unless we create________ less polluted world.

___alone in thelarge house, the little boy had to learn to survive by himself

Facing the poor grades, Maria is wondering what it ___ to learn English well.