Complete the sentences with at , on , or on . 1. They left ____ 3 o'clock. 2. I'm going to London ____ May. 3. We usually meet ____ Saturdays. 4. The whole family gets together ____ Christmas. 5. It was built ____ 19th century. 6. It's very cold here ____ winter. 7. Jessica was born ____ December 18th. 8. The temperature drops below zero ____ night. 9. The accident happened ____ Monday night. 10. I'll be back ____ an hour. Printable Answer key 1. at, 2. in, 3. on, 4. at, 5. in, 6. in, 7. on, 8. at, 9. on, 10. in