Considering your income, you should be able to ______ at least twenty dollars a week.
The river _____ are covered with trees is very long.
-----Tim, please don’t talk in class. -----Pardon? -----I _____ talk in class.
When Jack arrived, he learned Mary _____ for almost an hour.
The speaker mentioned some writers and books _____ were known to us.
-----I called you at about half past eight last night but nobody answered. -----Oh, I _____ in my office at that time.