Điền giới từ thích hợp: 1. He said the train would be leaving the station ............. 25 minutes. 2. My father met my mother ......... the war 3. Those men have been working on the motor ........... three hours now 4. The students have been here ......... the begining ......... the semester 5. She said she was going to returned to Nha Trang ....... the tenth of August 6. The train will leave the Hang Co Station ....... twelve minutes 7. Wait right here for me. I'll be away ...... 15 minutes. 8. Our boss, Mr. Thanh, has worked for thí company ........ the war 9. My sister and I make trips to nearby cities ....... time ...... time 10. Once ........... a while, I enjoy eating at a Chinese restaurant 11. Hoang's command of English is improving day .... day 12. I don't think Mr Thanh plans to stay in HN ......... very long 13. My father called to tell me to go home ........ once 14. We got there just ....... time to see the end of the program 15. We had taken a taxi in order to get to the meeting ......... time