A：You've traveled abroad a lot, Jim, so would you like to tell me something about clearing customs.
      吉姆，你经常出国旅游，能向我介绍一下关于通关的情况吗？

B：When you arrive in a country, you clear customs. A lot of countries have two channels: the green channel and the red channel. Some countries, like India, have three channels: the white channel, the green channel and the red channel.
      到达一个国家时要通关。许多国家的海关有两种通道：绿色通道和红色通道。还有些国家如印度有三种通道：白色通道、绿色通道和红色通道。

A：Then what are the differences between the green channel and red channel?
      那么绿色通道和红色通道之间有什么区别呢？

B：If you have more than the duty-free allowances or prohibited goods, you go through the red channel and declare them to a customs officer. If you otherwise have nothing to declare, you go straight through the green channel unless you are asked to stop by an officer. 如果你携带的东西超出免税的范围或属于禁带物品，你
      就得从红色通道通过并向海关官员申报物品。如果你没有需要申报的物品而海关官员又没有阻拦你，你就可以直接通过绿色通道了。

A：I see.I'm told that we'll have to state the purpose of going to a certain country, is it true?
      我明白了。我听说去一个国家时需要陈述旅行的目的，是吗？

certain的意思

B：That's right. People go aboard for different purposes: some for pleasure, some on vacation, some on business, and some for other purposes.
      是的。人们出国都各有目的：有的为了消遣，有的出去度假，有的是因公出差，有的是为了其他目的。

A：I'm going to New Zealand for sightseeing. What should I say if they ask about my purpose?
      我要去新西兰观光，如果他们问我旅行的目的我该怎么说呢？

B：Just saying "sightseeing" is OK.
      说"观光"就行了。

1. 肯定的;有把握的;毫无疑问的
    If you are certain about something, you firmly believe it is true and have no doubt about it. If you are not certain about something, you do not have definite knowledge about it.

    e.g. She's absolutely certain she's going to make it in the world...
           她坚信自己会出人头地。
    e.g. We are not certain whether the appendix had already burst or not...
           我们不敢肯定阑尾是否已经破裂。

2. 必然的;必定的;肯定的
    If you say that something is certain to happen, you mean that it will definitely happen.

    e.g. However, the scheme is certain to meet opposition from fishermen's leaders...
           然而，这项计划一定会遭到渔民领袖的反对。
    e.g. It's not certain they'll accept the Front's candidate if he wins...
           即便来自阵线的候选人获胜，他们能否接受他还说不准。

3. 确凿的；无疑的
    If you say that something is certain, you firmly believe that it is true, or have definite knowledge about it.

    e.g. One thing is certain, both have the utmost respect for each other...
           有一点可以肯定，那就是双方都非常尊重对方。
    e.g. It is certain that Rodney arrived the previous day.
           罗德尼肯定是头天到的。

4. 确实的;肯定的
    If you have certain knowledge, you know that a particular thing is true.

    e.g. He had been there four times to my certain knowledge.
           我确定他去过那儿4次。

5. 确切地;无疑地
    If you know something for certain, you have no doubt at all about it.

certain的反义词

    e.g. She couldn't know what time he'd go, or even for certain that he'd go at all...
           她不知道他何时走，就连他到底走不走都说不准。
    e.g. Hill had to find out for certain.
           希尔得弄个清楚。

6. 确保；保证
    If you make certain that something is the way you want or expect it to be, you take action to ensure that it is.

    e.g. Firstly, they must make certain that their pension needs are adequately catered for...
           首先，他们得确保他们能获得足够的养老金。
    e.g. To make extra certain, a police helicopter kept watch from the skies.
           为确保万无一失，一架警用直升机一直在空中警戒。

1. 某个;特定的
    You use certain to indicate that you are referring to one particular thing, person, or group, although you are not saying exactly which it is.

    e.g. There will be certain people who'll say 'I told you so!'...
           一定有人会说：“我怎么跟你说来着！”
    e.g. You owe a certain person a sum of money...
           你欠某人一笔钱。

2. 某些;一些
    When you refer to certain of a group of people or things, you are referring to some particular members of that group.

certain的解释

    e.g. They'll have to give up completely on certain of their studies.
           他们将不得不彻底放弃某些研究。

3. (用于人名前，表示不认识或了解很少)某个
    You can use a certain before the name of a person in order to indicate that you do not know the person or anything else about them.

    e.g. She managed to arrange for them to be hidden in the house of a certain Father Boduen.
           她设法安排他们藏在一个叫博迪恩的神父家里。

4. (品质、特点等)一定程度上的，有点儿
    You use a certain to indicate that something such as a quality or condition exists, and often to suggest that it is not great in amount or degree.

    e.g. That was the very reason why he felt a certain bitterness...
           那就是为什么他感到有些痛苦。
    e.g. There is a certain impatience among some of the soldiers...
           有些士兵有点儿不耐烦。