句法问题与it的意义

老师好，想询问这个句子“B shall not apply for intellectual property rights by making use of learning about the commercial secretes of A it has learnt to any extent.”里面后面的“it has learnt to any extent”是什么成分，it可以换成that吗？

B shall not apply for intellectual property rights by making use of learning about the commercial secretes ofA it has learnt to any extent.

划线部分为定语从句。先行词是 the commercial secretes ofA （A方的商业秘密）。

it 是人称代词，指代B方。关系代词that 由于作 has learnt 的宾语，被省略。it换成 that 没道理。

【翻译】B 方不能借助其已了解的A 方商业秘密来申请常识产权。