Поставьте глаголы, данные в скобках в правильную форму:
1. Metals (to use) by man after wood and stone.
2. Engineering metals (to use) in industry in the form of alloys.
3. Different metals (to produce) in different ways.
4. The first metal which (to produce) by people was copper.
2) using
3) producing
4) was produced
1) has been used
2) using
3) producing
4) was produced
Объяснение: