Public service ads,also PSAs,often _________ for free,_________ to educate people about health,safety or any other problem that affects public welfare.
We had to stay at home ________ a heavy rain.
You’d better have your bike ________, or it’ll get you into trouble.
--- Do you know our city at all? --- No, this is the first time I ________ here.
He told us ________ again.
---When will the plane leave? ---It ________ very soon.