They Were the Boy Scouts__________to help elderly people cross the streets.
The government has taken some measures to prevent more trees from _____.
Susan, _____ university student from Europe, teaches me _____ art in her spare time.
It was the first time Mary _____ such a big opening ceremony.
Today Bob contradicted Ms. Li, our math teacher, in class, _____ made her angry with him.
Many things that were once considered useful and _____, for example, tobacco, is now thought harmful.