My MP4 has disappeared. Who _______ have taken it away?
The new safety regulations were agreed on after _____ with the work-force.
His test results are not very _____. He does well one week and badly the next.
Scientists think they have _____ in their attempt to find the causes of some major dieases.
. If you ever have the _____ to go abroad to work, you should take it.
I'd like to take _____ of this opportunity to thank you all for your cooperation.