1. We studied earthquakes at school.
2. The tsunami in Thailand was a terrible accident for thousands of people.
3. Tornados happen very often in the USA.
1. Where do hurricanes always begin?
2. Which city has the most rain and floods?
3. How fast can a tsunami travel?
1. Holidaymakers should not litter in the forests.
2. Sometimes people don't survive in the earthquake.
3. The pollution of the environment was not discussed during the last UN summit.
утвердительные и положительные предложения - это одно и то же:-))