5035.oak(名)橡树、橡木
This table is made of solid oak.
这张案子是用实心橡木制作的。

5036.oath(名)宣誓、誓约；诅咒
Government employees swear an oath not to reveal official secrets．
政府雇员宣誓不泄露官方机密。

5037.obligation(名)义务；人情债
You are under no obligation to buy anything.
你不必非买什么东西不可。

5038. oblige(动)使感激：迫使
People who cannot find time for recreation are obtiged sooner or later to find time for illness.
挤不出时间休息娱乐的人迟早会被迫挤出时间养病。

5039.observant(形)善于观察的
Observant walkers may see red deer along this stretch or the road.
观察敏锐的步行者能在这一路段看到赤鹿。

5040.observation(名)观察；评论
Observations were made of the children at the beginning and at the end of pre-school and first grade．
这个观察是针对孩子们在学龄前和小学一年级开始和结束时的情况所做的。

5041.observatory(名)天文台、气象台
The stadium lights polluted the sky around the observatory.
体育馆的灯光使得天文台周围的夭空不那么适宣观测了。

5042.observe(动)观察；遵守
Every driver should observe the speed limit.
每个司机都应当遵守速度限制规定。

5043.observer(名)观察者、目击者
He was sent along as an observer.
他被派作观察员。

5044.obstacle(名)阻碍
when a big stone blocks the way,the brave view it as a stepping stone;the weak as an
obstacle.
大石拦路，勇者将它视为前进的阶梯，弱者将它视为前进的障碍。

5045.obstruct(动)阻隔、遮断
The crash obstructed tha road for several hours.
撞车事故把道路阻塞了几个小时。

5046.obtain(动)获得
He failed to obtain a scholarship.
他没有获得奖学金。

5047.obstinate(形)固执的
同义词stulbbom
He can be very obstinate when he wants to be!
他的强劲一上来，简直拗得要命！

5048.obvious(形)明显的
His nervousness was obvious right from the start．
他从一开始就显得十分紧张。

5049.obviously(副)明显地
Obviously，we don't want to spend too much monney.
很明显，我们不想花太多的钱。

5050.occasion(名)场合；机会；理由
I can remember very few occasions when he had to cancel because of ill health.
我记得他因为健康不佳而被迫取消的情况绝无仅有。

5051.occasional(形)偶然的
She likes an occasional glass of wine.
她偶尔喝杯酒。

5052.occasionally(副)偶尔
They occasionally go to a theater in these days.
这些日子他们偶尔去剧院。

5053.occur(动)发生；存在
后接介词to
Something unexpected occurred.
发生了一件出乎意料的事。

5054.occurrence(名)事件
Satellites have extended the power of communications to report events at the instant of occurrence.
卫星使通讯具有了报导即时发生事件的能力。

5055.odd(形)古怪的；奇数的；奇持的
同义词pecliar
I find it odd that she hasn't written to us.
我觉得她没写信给我们有点奇怪。

5056.odds(名)胜算；可能的机会
惯用复数
The odds are heavily against him.
他成功的几率很小。

5057.offer(动)(名)提议，提供
(动):Josie had offered her services as a guide.
乔西曾表示愿意当向导。
(名):You can't just turn down offers of work like that.
人家给你工作，你不能就那样一一谢绝呀。

5058.offspring(名)子孙、后代、后裔
The stomic bomb is the offspring of the 20th century physics.
原子弹是20世纪物理的产物。

5059.onset(名)进攻、袭击
The fierce onset of the enemy broke the ranks of the army．
敌人的猛烈攻击致使全军大乱。

5060.opera(名)歌剧
Does opera interest you?
你对戏剧感兴趣吗？

5061.operate(动)操作、见效
Solar panels can only operate in sunlight.
太阳能电池板只能在日光下起作用。

5062.operation(名)手术；经营；运算
Will need to have an operation?
我需要动手术吗？

5063.operational(形)操作上的、管理的
The new airport should be fully operational by the end of the year.
新机场应在年底前全面投入运营。

5064.operator(名)接线生
Dial 100 and ask for the operator.
请拨100找接线员。

5065.opinion(名)意见、评价
We were invited to giVe our opinions about how the work should be done．
我们应邀对于如何开展工作提出意见。

5066.oponnent (名)对手
Someone has said that thare's no etarnal friend or opponent in the business cicles.
有人曾说过，在商场上，没有永远的朋友,也没有永远的敌人。

5067.oppose(动)反时
This party would bitterly appose the reintroduction of the death penalty.
该党会强烈反对恢复死刑。