Most environmental problem exist because___measures for preventing them were not taken in the past
The man insisted __________ a taxi for me even though I told him I lived nearby.
Isn't it time you got down to __________ the papers?
In some parts of London, missing a bus means __________ for another hour.
You can't imagine what great trouble they have __________ the problem __________.
The boy was criticized for forgetting __________ his textbooks to school.