The new system needs to be in operation for five months ________ it can be updated.
A．as B．while
C．before D．once
We can't wait any longer ________ we'll miss the plane.
A．or B．but
C．so D．yet
House prices vary from place to place and are usually high ________ there are famous schools.
A．when B．since
C．where D．whether
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
