Ответ:

1. is; was crowded

2. are; were learnt

3. are; were protected

4. is; was made

5. are; were fed

6. are; were worn

7. are; were shown

8. do not have a verb to be in the sentence, thus cannot be converted to Past Simple

9. is; was always cooked

10. does not have a verb to be in the sentence, thus cannot be converted to Past Simple