The first textbooks __________ for teaching English as a foreign language came out in the 16th century.
John _____ knowledge of radio just by staying around the radio station.
With sufficient scientific information a manned trip to Mars should be _____.
At first the institute refused to purchase the telescope, but this decision was _____ revised.
_____ inviting guests and not treating them properly!
It isn't so much whether he works hard; the question is whether he works _____.