The room is in a terrible mess; it __________ have been cleaned.
Finally they found out the truth ________ he had gone abroad with a lot of money.
We expressed the hope ________ they would come and visit China again.
Everyone at the meeting agreed to the suggestion ________ a new bridge ________ built across the river.
The belief ________ people find it more convenient to stop on Sundays ________ in the research.
Tom came back with a message ________ there would be a test soon.