VI. Перепишите предложения. Подчеркните инфинитив, установите его функцию и переведите предложения:
1. They promised to supply us with the necessary equipment.
2. The purpose of this book is to describe certain properties of metals.
3. The experiment to be carried out is very important for our research.
4. To convert chemical energy into electrical energy we must use an electrical cell.