Steve was busy clearing the cups and dishes from the table ________ others were playing.
A．until B．if
C．since D．while
________ it is, the boy never seems to be able to finish it off.
A．However interesting a book
B．Whatever interesting a book
C．How interesting a book
D．What an interesting book
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
