5. arrived , were watching
6.collected
8. don't want , am waiting
9. viet sai chu already nha ban :" alreadly"
11. was doing
13. walked
bai 2
cau 6: reuse cua ban chua chia thi nha:"reuse"->"reused"
cau 7: speak cua ban viet sai thi nha;"speaken???"->"spoken"
cau 8: sai-> the classroom window has been broken by the boy.
cau 9: sai-> this letter was gotten this morning.
bai 3:
cau 3: can -> could nha ban