unconscious adj.不省人事的；未发觉的；无意识的。通常用短语be unconscious of 或be unconscious。

　　【相关链接】

　　conscious adj.意识到；有意识的

　　consciousness n.知觉；意识

　　unconsciously adv.无意地；不知不觉地

　　unconsciousness n.昏迷；无知觉状态

　　4.be on (one's)guard 保持警惕

　　【典型例句】

　　The soldiers are on guard around the whole palace in case terrorists attack.

　　士兵们围绕整个皇宫站岗，以防恐怖分子袭击。

　　Do you know the sentry on guard?

　　你认识值勤的哨兵吗？

　　【相关链接】

　　be off guard 不谨慎；不提防

　　guard against 防范；提防

　　keep guard over sth./sb.守卫；看守

　　5.be busy (in) doing sth.忙于做某事

　　【典型例句】

　　In big cities you will see people busy coming and going in the street.

　　在大城市里你会看到街上人们来来往往。

　　He is busy in raising birds in his spare time.

　　他空闲时间忙着养鸟。

　　【相关链接】

　　be busy with sth.忙于某事　例如:

　　When I went to visit her,she was busy with her novel.

　　我去拜访她时，她正在忙着写小说。

　　6.involve vt.包括;涉及

　　【典型例句】

　　There was a serious incident involving a group of youth.

　　有一起严重的事件涉及到一群年轻人。

　　The matter is serious because it involves your reputation.

　　这件事很严重，因为它影响到你的声誉。

　　This lesson involves a lot of work.

　　这一课有很多需要做的工作。

　　【相关链接】

　　be involved in/with 与......有关；关注；参与

　　I was so involved in my book that I did not hear your knock.

　　我全神贯注在看书，没听到你敲门。

　　All the children were involved in the school play.

　　所有的孩子都参加了学校排练的戏剧。

　　7.hold up 举起；阻碍,使停顿

　　【典型例句】

Can you hold up the stone for some minutes?