5.Is ____ necessary to complete the design before National Day?
John said he had been working in the office for an hour, _______ was true.
The science of medicine _______ progress has been rapid lately is perhaps the most important of all the science.
Is this the reason _______ at the meeting for his carelessness in his work?
This is Mr. White, _______ I think has something interesting to tell you.
_______ has been announced, we shall have our final exams next month.