Robert is said _______ abroad, but I don’t know what country he studied in.
You shouldn’t keep silent when __________.
---The meeting has begun and __________ he will come.---Of course, he is sure to come. He’ll speak at the meeting.
—What do you think of this matter? —This is a matter of __________ importance. I think.
Some countries are increasing their use of natural gas, and other forms of __________.
Though he is __________ worker, he works very hard.