While ________ the street, he was hit by a car.
We hadn't met for 20 years, but I recognized her_____ I saw her.
________evidence that language acquiring ability must be stimulated.
The professor could hardly find sufficient grounds _____his arguments in favor of the new theory.
A survey was carried out on the death rate of those who were infected by SARS, ________were surprising.
In recent years much more emphasis has been put______ developing the students productive skills.