27. People have become aware ______the fact that carbon dioxide, poison to the environment, contributes_____ air pollution.
Eric _________ go camping with us this Sunday, but he isn’t quite sure yet.
The movie star didn’t _________ until the crazy fans had waited for almost two hours.
------ How about going camping this weekend? ------ Good idea ! ____________.
If my father ______here now, he _____ tell me what to do. But he left home just one hour ago.
Guilin is a beautiful place ______ you can enjoy yourself a lot.