Students should pay attentions to ________ the teachers in class.
I think this is the most interesting thing _____ has happened to us .
--- I’d like to introduce my best friend to you , Peter .---- Thank you , Lucy . But we __________already .
_____ out your love . The world will become a nicer place to live in .
Success will belong to those ___ never say impossible ..
----- Have you heard of Earth Day ?----Yes . The first Earth Day ______ in 1970 to educate us to protect our planet .