o'clock
［误］ It's ten past five o'clock.
［正］ It's ten past five.
［析］ o'clock所表达的时间是正点，如果要表达的时间是几点几分或差几分几点都不能用o'clock.
once
［误］ Please come and see me once.
［正］ Please come and see me one day.
［析］ once用来谈论过去的事情，而不能谈论未来。如果要谈及未来要用one day, some time等。
［误］ I met him one time when I was a student.
［正］ I met him once when I was a student.
［析］ 英语中一次应用once而不用one time，二次要用twice而不用two times.
one
