What ______ public is concerned about is whether medical workers and scientists will be able to find _____ cure for this new disease in a short time .
According to a UN report, one third of the world population have no ____ to clean drinking water and health care.
It is likely that water is not ____ endless resource, nor ____ that can be made once more.
How long ______ teaching? Forty years.
An operation is usually performed by a ______.
He is the manager of the factory. He is ______ it.