根据句意和所给中文写出句中所缺的单词。

1. First, please _________ (介绍) yourself to us all, OK?

2. Something should be done to protect the ________ (环境) in our hometown.

3. After _________ (检查) the computer, he told me there were no tickets.

4. Smoking will _________ (当然) do harm to your health.

5. There will be an exciting football match between China and Japan on _________ (频道) 5 tonight.