Mr. Zhang has retired already. He in our school for over thirty years.
| A．has worked | B．had worked | C．worked | D．was working |
It will be another 50 years ______ our country is expected to reach the level of a medium developed country.
| A．since | B．before |
| C．that | D．when |
Jerry has promised to keep the secret, so he won't tell anyone ________ asked to.
| A．until | B．now that |
| C．unless | D．even though |
The movie Life of Pi is so attractive that it holds the audience's curiosity ________ the story reaches the end.
| A．until | B．before |
| C．after | D．when |
________ H7N9 is a deadly virus, it is still safe to eat thoroughlycooked chicken.
| A．Until | B．While |
| C．If | D．Since |
I will accept Guy coming with us, ________ he pays for his own meals.
| A．only if | B．so that |
| C．ever since | D．even though |