It is uncertain ______ the experiment is worth doing .
| A．where | B．that | C．whether | D．how |
After Peter died, George ______________ the story of their friendship in a book.
| A．added up | B．set down | C．turned out | D．get along with |
The _____ language used in most international organizations is English.
| A．official | B．native | C．frequent | D．separate |
--- Hello! Is Mr. John in the office?
--- Yes. But I’m sorry. He is busy _________ and can’t speak to you.
| A．at once | B．at present | C．at the end | D．at first |
As a young man, there was __________ time __________ I hated to go to school .
| A．a; that | B．a; when | C．the; that | D．the; when |
—I am leaving for the States tomorrow, Caroline!
—______
| A．Take your time. | B．That’s OK. | C．Well done! | D．All the best! |