We must try our best to the river being polluted any more.
After a knock at the door, the child heard his mother’s voice ______ him.
Pop music is such an important part of society ______ it has even influenced our language.
The little boy came riding full speed down the motorway on his bicycle. ______ it was!
With the help of high technology, more and more new substances ______ in the past 10 years.
—Sorry, I made a mistake again. — ______. Practice more and you’ll succeed.