Riddle: What is it that occurs once in a second, once in a month, once in a century, yet not at all in a year or a week?
举一反三
- When he was a solider abroad, Edward would always contact his family through telephone calls, but usually ________________. A: only about once a month B: only about once a year C: only about once a week D: only about once a day
- 同时: all at once|all once|at all once|at once
- The phrase "once in a blue moon" in last line refers to______. A: all at once B: once for a long time C: once in a while D: once and for all
- How often did Mike go to the barber's? () A: Once a day B: Twice a month C: Three times a week D: Four times a year
- Once a year,on the