小升初英语语法：Be的四个功能归纳

　　be是一个多功能动词，在初级英语里可见四种用法：

　　功能一，系动词be

　　be为连系动词，中心词义是是，句型为主+系+表结构。be的形式常用am, is, are(现在式);was, were(过去式);will/can/may/must be(助动词/情态动词+原形);have/has/had been(助动词+过去分词)等。如：

　　To help animals is helping people.(一般现在时)

　　The twins were very busy yesterday.(一般过去时)

　　It will be sunny tomorrow.(一般将来时)

　　She has been ill for over a week.(现在完成时)

　　功能二，助动词be

　　助动词be，无词义，辅助主要动词一起在句中作谓语动词。用法如下：

　　1. be+doing：构成进行时态，有现在和过去两种进行时态。如：

　　The girls is reading and copying the new words now.

　　Young Tom was always asking questions and trying out new ideas.

　　2. be+done：构成被动语态(主语是动作的承受者，done必须是及物动词)。如：

　　Tea is grown in my hometown.(一般现在时的被动语态)

　　This building was built three years ago.(一般过去时的`被动语态)

　　Our classroom has been cleaned and tidied already.(现在完成时的被动语态)

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