A、He often teaches children what to do during a fire. B、He teaches Spanish in a San Francisco community. C、He provides oxygen ma

　　One of the greatest heartbreaks for firefighters occurs when they fail to rescue a child from a burning building because the child, frightened by smoke and noise, hides under a bed or in a closet and is later found dead. (16) Saddest of all is when children catch a glimpse of the masked firefighter but hide because they think they have seen a monster. (17)To prevent such tragedies, firefighter Eric Velez gives talks to children in his community, explaining that they should never hide during a fire. He displays firefighters’ equipment, including the oxygen mask, which he encourages his listeners to play with and put on. "If you see us," Velez tells them, "don’t hide! We are not monsters. We have come to rescue you." Velez gives his presentations in English and Spanish. Growing up in San Francisco, he learnt Spanish from his immigrant parents. Velez and other firefighters throughout North America, who give similar presentations, will never know how many lives they save through their talks. (19) But it’s a fact that informative speaking saves lives. For example, several months after listening to an informative speech, (18) Pete Gentry in North Carolina rescued his brother who was choking on food, by using the method taught by student speaker, Julie Perris. In addition to saving lives, informative speakers help people learn new skills, solve problems and acquire fascinating facts about the exciting world in which they live.
　　16.  Why do some children trapped in a burning building hide from masked firefighters?
　　17.  What does the passage tell us about firefighter Eric Velez?
　　18.  What do we learn about Pete Gentry?
　　19.  What message is the speaker trying to convey?