In the school where I study English ____ .
The passer-by jumped into the cold water to save the _____ boy, who cried for help, but it was too late and the boy was _______ at last.
The computer system _____ suddenly while he was searching for information on the Internet.
Cycling is highly _____ to people’s health and the environment.
I recognize her __I met her at the airport, although we haven’t seen each other for ten years.
Unless ________ to speak, you should remain silent at the conference.