1. Sometimes the weather in England changes very quickly. (Present simple active.)
2. This article is often reffered to. (Past simple active).
3. What are you doing here? — I'm waiting for my friend. (Present simple active).
4. He has not been seen for a long time.( Present Progressive passive)
5. I have already done my work. (Past simple active).
6. They spent their holidays in the mountains when they were students. (Past simple active).