Question

我想知道他们是否已经去过那家新的书店。

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Answer

I wonder if they have been to that new bookshop.

【解析】

分析句子可知，这是if引导的宾语从句，主句是一般现在时，其主语是：我I；谓语是：想知道wonder；从句是现在完成时，引导词是：是否if；其主语是：他们they；谓语是：已经去过（已回来）have been to；宾语是：那家新书店that new bookshop。宾语从句遵循陈述句语序，组成句子后，故答案是I wonder if they have been to that new bookshop.