a fine line

在某些情况下，建设性批评和个人攻击之间只有细微差别。

In some situations, ___a ___fine ___line separates constructive criticism from personal attack.

科幻与科学事实之间有一条微妙的界线。

There is ___a ___fine ___line between science fiction and scientific fact.

实用的人工智能与侵犯隐私之间有一条微妙的界线。

There is ___a ___fine ___line between useful artificial intelligence and an invasion of privacy.