1. It had once been the home of a wealthy nobleman.
2. We tend to meet up for lunch once a week.
3. He once told an interviewer that he didn't even like rock music.
4. Once wholesale prices are deregulated, consumer prices will also rise.
5. He took off at once and headed back to the motel.
6. The car passed over the body twice, once backward and then forward.
那辆车把那人来回轧了两次,先是倒着轧的,再是往前开着轧的。