这个句子如何转换呀?The children have arrived in Beijing by plane.（改为否

肯定句变否定句 十三点需要注意
肯定句改为否定句是英语句型改写的一种常见而典型的题型.改写时一般应在系动词be,情态动词can,may,must等或助动词have,has等后加上否定词not,当句中不出现这些词时则应借助于助动词do（es）或did来帮助.例如：
His brother is a teacher．→His brother isn't a teacher．
A dolphin can speak．→A dolphin can't speak．
I got up at seven this morning．→I didn't get up at seven this morning．
在进行此类句型改写时同学们应注意以下几个方面：
一、have（has）除了表示“有”或用作助动词时可在其后加上not变为否定句外,表示其它意义时只可借助于助动词 do（es）或did来构成否定.例如：
Lucy has a nice bike．Lucy doesn't have a nice bike．（或：Lucy hasn't a nice bike．）
The Greens have arrived in China．→The Greens haven't arrived in China．
二、肯定句中含有some时,一般应将some改为any,含有some-所构成的复合不定代词及副词时应将其改为含any-的复合不定代词或副词.例如：
They are going to pick some apples on the farm．→They aren't going to pick any apples on the farm．
Those people have done something to protect the environment．→Those people haven't done anything to protect the environment．
Last year they went somewhere in China．→Last year they didn't go anywhere in China．
三、肯定句中含有and连接两个并列成分时,一般应将and改为or.例如：
The clock has feet and legs．→The clock doesn't have feet or legs．（此句也可改为：The clock has no feet and no legs．此时的and不可改为or．）
四、肯定句中含有always时,应将always改为never以变成完全否定形式；而肯定句中含有almost时,应将almost改为hardly以变成完全否定形式.例如：
Uncle Wang always goes to work on foot．→Uncle Wang never goes to work on foot．
Dreams of finding lost treasure almost came true．→Dreams of finding lost treasure hardly came true．
五、含有a few,a little等的肯定句改为否定句时可将a few,a little改为few,little表示否定意义.例如：
Dad had a little bread for breakfast this morning．→Dad had little bread for breakfast this morning．
Yesterday I bought a few English books．→Yesterday I bought few English books．
六、含有表示“也”之意的too,also的句子,改为否定句时应将too,also改为either.例如：
Lily likes swimming,too．→Lily doesn't like swimming,either．
Last Sunday Han Mei also went to the dolphin show．→Last Sunday Han Mei didn't go to the dolphin show,either．
七、含有often的肯定句,改为否定句的方法是将often改为seldom.例如：
Jim often rings me up．→Jim seldom rings me up．
The twins often watch TV in the evening．→The twins seldom watch TV in the evening．
八、含有everything,everybody等的肯定句应将它们分别改为nothing,nobody,使其变为否定句.例如：
Everything turns green now．→ Nothing turns green now．
Everybody can help you．→Nobody can help you．
九、祈使句的否定句应在动词原形前加上否定词don't.例如：
Tell her to stay at home,please．→Don't tell her to stay at home,please．
十、“let ＋宾语＋动词原形”结构的否定形式可在后面的动词原形前加上否定词not（也可在let前加Don't）.例如：
Let the children do as they like．→Let the children not do as they like．
十一、当肯定句中含有already时,改为否定句应将already变为yet.例如：
We have decided when to start already．→We haven't decided when to start yet．
十二、在I（We）think等词后跟上一个从句时,将其改为否定句应将think等词改为否定形式,而不应将后面的句子改为否定形式.例如：
I think he can get there tomorrow morning．→I don't think he can get there tomorrow morning．
十三、肯定句中含有all时,改为否定句应将all改为none而将其变为完全否定形式；肯定句中含有both时,改为否定句应将both改为neither而将其变为完全否定形式；肯定句中含有both．．．and．．．结构时,应将其改为neither．．．nor．．．而将其变为完全否定形式.此时,应注意谓语动词的人称和数的变化.例如：
All of them have learnt surfing from me．→None of them have learnt surfing from me．
Both of his parents know how to search the Internet．→Neither of his parents knows how to search the Internet．
Both the digital camera and the computer are Jack's．→Neither the digital camera nor the computer is Jack's．

The children haven't arrived in Beijing by plane.