---Good morning,Doctor Brown’s office.---Hello, this is Tom Smith. Could you please tell Doctor Brown I ? My car start.
Is______necessary to change trains at Beijing?
When and where to build the new power station ______ yet.
_____is a good of exercise for both the young and the old.
________more attention, the work would have been done better.
Most air pollution is caused by the burning of _________ like coal, gas and oil.