The US President Obama told the students that he ______ by a single mother who were strict with him and wished him great success in his studies.
So difficult ___it to work out the problem that I decided to ask Tom for advice.
He ____ have finished his work; Otherwise, he would.not be enjoying himself by the seaside.
With more forests being destroyed, huge quantities of good earth_______ each year.
_______in the forests for nearly a week, the two students were finally saved by the local police.
The place______ the bridge is supported to be built should be _____ the cross river traffic is the heaviest