导读：词组能有效的帮助大家提高完型和句子的理解与写作质量，为保证大家能够灵活运用考研重点词组，社科赛斯李梅老师特配以相应的例句，帮助大家更快地获得更高的分数。
621. on earth 究竟，到底
What on earth had Luke done?
卢克究竟做了什么？
622. on fire 起火着火
The workshop is on fire.
车间[工厂]起火了。
623. on foot 步行
I go to school usually on foot.
我上学通常是走路去。
624. out of contact with 与...失去联系
I have been out of contact with her for three years.
我与她失去联系已有三年。
625. on hand 在场，在手边
She was not on hand.
她不在场。
There is a dictionary on hand to help during his private study periods.
他学习时总是把词典放在手边。
626. on occasion 有时，间或
You have on occasion surprised people.
你有时使人们感到诧异。
627. out of control 失去控制
The fire is burning out of control.
熊熊燃烧的大火正在失去控制。
628. on purpose 故意地
Maybe he does this on purpose?
也许他是故意这么做的？
629. on sale 出售，廉价出售
All tickets go on sale this Friday.
所有票在本星期五开始销售。
630. on schedule 按时间表，准时
The goods arrived on schedule.
货物已如期运到。
