The answer is: A
Explanation
According to Section 22 of the Indian Evidence Act, 1872, oral admissions as to the contents of a document are not relevant, unless and until the party proposing to prove them shows that he is entitled to give secondary evidence of the contents of such document under the rules hereinafter contained, or unless the genuineness of a document produced is in question.
Secondary evidence is defined in Section 63 of the Act as including oral accounts of the contents of a document given by the person who has himself seen the document.
Therefore, the correct option is A: when given by a person who has seen & read the document. This is because such a person can give secondary evidence of the contents of the document, provided he satisfies the conditions mentioned in Section 22. The other options are not correct, as they do not fall under the definition of secondary evidence.