Раскройте скобки употребляются в Past Simple или Past Continuous

12. I (to walk) along the street with my friend when a tram (to pass). 13. She (to look) out of the window when I (to see) her. 14. We (to answer) the teacher's questions when the headmistress (to enter) the classroom. 15. They (to drink) tea when I (to come) home. 16. He (to walk) along the river when a boat to go) out. 11. He (to read) on the sofa when I (to come) in and (to sit) down beside him.