The box is .
A. too heavy for me to carry
B. too heavy for me to carry it
书上说A当然正确，但说B也是正确的。为何呢？这是不定式的悬空结构吗？
麻烦老师解析一下，谢谢！
不定式悬空结构，仅限于这类：
The question isdifficult to answer.
difficult to answer 应整体看作is 的表语。这个时候的不定式to answer 是表语的一部分。
假如difficult 之前加 too，那样不定式变成了结果状语。就能说：
The question is too difficult to answer it.
The question is too difficult to be answered.
The question is too difficult for me to answer it.
The question is too difficult to be answered by me.
所以，The box is too heavy for me to carry it. 也正确。
