Fill in the gap with the suitable prepositions: l'm only be ... town for 3 days

Fill in the gap with the suitable prepositions
1. l'm only be                 town for 3 days
2. l'll pick you               at your hotel
3. The lava was pouring                   when we flew overhead
4. The heads of four American presidents are carved              rock
5. What is special                  Mount Rushmore ?
6. He is always complaning                    the heaviness of my suitcase
7. Can l use your computer                    one hour ?
8. Could you solve this math problem                 me?
9. You could save some money                   used things
10. My class won the first prize                  collecting cans