根据句意和汉语注释，在答卷标有题号的横线上，写出单词的正确形式。
We hope you can _____________ (收受) our invitation and join us.
We need the correct ______________ (地址) of our American friends so that they can soon get our letters.
You can understand his report ___________ because there are few new words. (不费力地)
All of us should _____________(行动) to protect our earth.