16. A book on space travel (publish) ........................... last month?
17. Millions of trees (destroy) ..................................by pollution every year.
18. I (finish)………………. my homework ten minutes ago.
19. My report (finish)……………….. ten minutes ago.
20. Every day the streets (clean)…………….. by these cleaners.
21. The cleaners (sweep) …………………. the streets every day.
22. We (meet)………….. Nam at the airport last night.
23. Nam (meet)……………..at the bus station by his friends two days ago.
24. They (build)……………. a new bridge across this river now.
25.  Now two new parks (build)…………….. in Yen Bai city.