6 .I (cook) while my sister (wash up) 7. She (sleep) at 9 o ^ clock yesterday.8. I (write) a letter yesterday.9.When the iesson (begin). all the pupils ( sit) at their desks.10. He ( write ) this novel many years ago..
6. was cooking, was washing up 7. was sleeping 8. wrote 9. began, were sitting 10. wrote