Write questions using the passive. Some are present and some are past.

Решение:

1. Ask about glass. (how/make?) How is glass made?
2. Ask about television. (when/invent?) When was television invented?
3. Ask about mountains. (how/form?) How are mountains formed?
4. Ask about DNA. (when/discover?) When was DNA discovered?
5. Ask about silver. (what/use for?) What is silver used for?

Ответ: How is glass made?; When was television invented?; How are mountains formed?; When was DNA discovered?; What is silver used for?.