Вставьте арктикли a/an or the (или не ставьте где не нужно)

1) We have _ big dog. _ dog is very clever.
2) My friend has _ very good computer.
3) This _ boy is big. He is _ student.
4) There is _ very big piano in _ hall
5) This is _ tree and that is not _ tree. It`s _ bush.
6) I am _ boy. I am _ pupil. I learn at _ school
7) My sister is at _ work. She is _ secretary. She works at _ large office
8) This is _ veru difficult question. I don`t know _ answer to it.
9) Do you see _ little girl with _ big ball is her _ hands. She is _ pupil of our _ school
10) There was _ beautiful flowers in this _ vase yesterday. Where is _ flower now?