Question

请分析这句话的语法成分

that's about as effective as brushing dirt under a carpet
that主语，is是系动词，然后呢？

Answer 1

That's about as effective as brushing dirt under a carpet.
参考译文：这几乎起到和在地毯下面清洗污垢一样的（副）作用。
句子主干部分为主系表结构：That is （about as） effective
That 主语，指代前文提到的内容；is 系动词，谓语；effective表语。
about是程度副词，意为“几乎”作状语。as...as结构中的第一个as也是副词作状语。
as brushing dirt under a carpet as引导的比较状语从句。

Answer 2

除了你已分析过的外，as effective 是表语，about 副词作状语，修饰as effective ，as brushing dirty under a carpet 比较状语

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