It cost her 100 yuan to buy the book.改为否定句
问题描述：
It cost her 100 yuan to buy the book.改为否定句
答
It 【didn't】cost her 100 yuan to buy the book.
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祝你学习进步,更上一层楼!(*^__^*)】不是用will not 吗不用， 因为原句是一般过去时