Please the radio. I want to listen to the news.

Nowadays school bus safety has drawn much attention nationwide for children’s safety is _______ worries parents most.

Some plants are so difficult to grow that they can only ______ in a perfectly clean environment.

In the lecture, little Tom kept silent all the time unless _________ to express his opinion.

Excuse me, sir. But nobody _____ smoke here in the lift! — Sorry! I didn’t see the sign.