Действие кислот на индикаторы

Довольно таки примитивно, но зато убедительно))
1. I don't worry about problems very much. I always have optimistic opinion.
2. I think that the age of communication has begun with the invention of computer.
3. People should take care about nature and especially about endangered animals.
4. Space discoveries can recently change our conception about world.
5. Cancer is a very serious and dangerous desease. Every year it kills millons of people.
6. Nowadays supercomputers are the top of electronic technology.