n5 "The test of admissibility of extrinsic evidence to explain the meaning of a written instrument is not whether it appears to the court to be plain and unambiguous on its face, but whether the offered evidence is relevant to prove a meaning to which the language of the instrument is reasonably susceptible." (Pacific Gas & E. Co. v. G. W. Thomas Drayage etc. Co. (1968) 69 Cal.2d 33, 37 [69 Cal.Rptr. 561, 442 P.2d 641]; accord, Delta Dynamics, Inc. v. Arioto (1968) 69 Cal.2d 525, 528 [72 Cal.Rptr. 785, 446 P.2d 785].)  [Editorial note: In quoting from Pacific Gas & E. Co. v. Drayage, this footnote fails to refer to fn. 8 of the Drayage opinion, which reads: "Extrinsic evidence has often been admitted [in cases where language is reasonably susceptible to more than one meaning] on the stated ground that the contract was ambiguous.  This statement of the rule is harmless if it is kept in mind that the ambiguity may be exposed by extrinsic evidence that reveals more than one possible meaning."   In the Drayage opinion, that footnote was dictum, i.e. not necessary to the reach the result in that case, because language being interpreted in the Drayage case was ambiguous on its face.  Does the Tahoe court ignore the footnote because it is dictum or because it is inconvenient to the result that it wishes to reach?]  

    Defendant did not object at trial to the extrinsic evidence, and thus cannot posit error upon its receipt by the trial court. This failure to object, however, does not bar her from contending on appeal that the extrinsic evidence is irrelevant since the assignment is not reasonably susceptible of being construed as a mortgage. (See part 2 of this opinion.)