. One third of the area ______ covered with trees. About seventy percent of the trees ______ been planted recently.
Many workers were organized to clear away remained of the World Trade Center.
The organization broke no rules, but ______had it acted responsibly.
A survey was carried out on the death rate of those who were infected by SARS, ________were surprising.
In recent years much more emphasis has been put______ developing the students productive skills.
_____ of water makes Death Valley a desert, but it is by no means devoid.