the secret is which can not be said
有,which 引导宾语从句的,这里它前面没有先行词
所以可以改成what
the secret is what can not be said
或者
the secret is that which can not be said
the secret is which can not be said
有,which 引导宾语从句的,这里它前面没有先行词
所以可以改成what
the secret is what can not be said
或者
the secret is that which can not be said