Explanation:

- Section 94 of the Indian Evidence Act deals with situations where language of a document is plain, and external evidence is not allowed to explain it.

- Section 80 relates to the presumption as to documents produced as records of evidence, not agreements varying document terms.

- Section 86 deals with the presumption as to certified copies of foreign judicial records, not about varying document terms.

- Section 99 specifically deals with who may give evidence to prove any fact that would entitle a person to a decree or order varying the document.