根据句意及首字母提示补全单词。

1. We've been doing experiments for 24 hours without a b_____.

2. F_____ , they caught the last bus last night.

3. Hosting the World Expo successfully was great e_____  in Chinese history.

4. Do you know when the Red Cross S_____ of China was founded?

5. Heroin (海洛因) is a kind of hard d_____.

6. All the students are present, nobody is a_____.