兩個is連用，文法有錯嗎？

Whose book it is is not important.= used in oral English not written English

Whose book is it ? It is not important = correct

or

Better rewrite the sentence as following

It is not important whose book it is.= best

其實這句文法並沒有錯，因為whose book it is是一句子句，作為名詞用，是名詞子句，因此，我們只需看它為名詞

Whose book it is意思是：這是誰的書
因此Whose book it is not important可以看為　noun (whose book it is) + verb(is+ 否定副詞not) + adj (important)，是完全合乎英文文法

而Whose book it is is not important.（意思是：這是誰的書，並不重要）

希望幫到你！

Something is not important.
What is that something? Whose book it is.

Inland Ireland Sea Searching
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I I S S
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Invisible Sea Identibilita Sailing

Whose book it is? lt,s not important.
因為1句,不可有兩個verb.就算用,都要有不定式或動名詞.而這句沒有.

這句應該是Whose book it is? lt,s not important.

前句問這本書是誰人的?後句說這不重要。

何況若用不定式或動名詞,句子就會變成:

Whose book it is not to be important.
or
Whose book it is not being important.

真怪!

Whose book is it ? It's not important.

有點怪怪地,我覺得成這樣會好些......

Whose book is it ﹖ is not important.