Complete the following passage with the words or phrases in the box. (将下列单词或词组填入空格，每空格限填一词。)                                 

A. dangerous B. safe C. again D. be ready to E. put out

Henry is a firefighter in Seattle. Seattle had a big fire about 100 years ago. Most of the city was burnt down to the ground then. Henry says he doesn't want that to happen . Henry works eight hours a day. When he is on duty(值班), he has to answer an alarm at any time. Most of the alarms are for small fires. Firefighters can the fires in a few minutes. There are also a few false alarms. When the firefighters arrive there, they find that there isn't any fire at all. Big fires are very . Sometimes, Henry has to go into burning buildings to save other people.