It does not prescribe what a user of English must or must not write or say, but gives sufficient guidance for the reader to make his or her own decisions.

本书并不企图告诉读者在写或说英语时必须遵循何种规则，而只是对读者提供充分的指导，帮助读者自己作出决定。

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Aiming at a familiar and simple constraint that some items must or must not present in rules, a fast clipped-transaction-based constraint association-rule mining algorithm was put forward.

针对一类常见而简单的规则中有项或缺项的约束，提出了一种基于事务数据修剪的约束关联规则的快速挖掘算法。

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Paintings must have rigid stretchers so that the canvas will be taut, and the paint must not deteriorate, crack, or discolor.

画必须有坚硬的画架，这样画布才会绷紧，而且颜料不能变质、开裂或变色。

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It may well be, Mr Wollheim says, that you cannot lay down in advance what art must or must not look like.

ECONOMIST: Contemporary-art criticism: Art��s dead; long live art | The

Which is that the actions that Apple must or must not perform in order to be ethical will differ according to the ethics of the person doing the calling and petitioning.

FORBES: Calling for an Ethical iPhone 5

They must not have had a UK top 20 single or album by 14 November 2010 and must not already be famous, for example by featuring in the final stages of a TV talent show or being a member of a successful band.

BBC: Sound of 2011 list revealed