全句语法树 (Syntax Tree)
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让步状语从句
While instant messaging allows for quick updates
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主句
it is crucial to remember that professional emails...
↳
形式主语
it
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系表结构
is (系) crucial (表)
↳
真正主语
to remember (不定式短语)
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宾语从句
that professional emails require a more formal tone
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时间/条件状语
especially when addressing clients or senior management.