The time he has devoted in the past 10 years________ the disabled is now considered________ of great value.
Every few years, the coal workers their lungs X-rayed to ensure their health.
The plan _________ just because people were unwilling to cooperate (合作).
Jack, I’m afraid I’ll turn to you.I think chemistry is _______ physics.
Not until then did I find it _____ to do the job that way.
Most of the professors _____ to our school were from South Africa.