it was found to be over thirteen feet long 请问to be如何理解和解释,

问题描述:

it was found to be over thirteen feet long 请问to be如何理解和解释,

我给你一个简单的方法:
We found that it (某一物体) was over thirteen feet long
over== more than
we found + 句子 (宾语从句)
it was found to be over thirteen feet long (简单句)