Which of the following is an example of a questioned document?

A questioned document is typically one whose authenticity or origin is disputed and needs to be examined to verify its legitimacy. In this context, a forged signature on a contract exemplifies a questioned document because it directly raises issues regarding authenticity and the true identity of the signatory. The intent behind the forgery is to mislead or commit fraud, necessitating forensic analysis to confirm whether the signature was genuinely made by the person whose name appears on the document.

The other examples provided do not inherently present the same issues regarding authenticity. A certified birth certificate, while it may be questioned in some scenarios, is generally accepted as a legitimate document once it is authenticated. A letter without a sender's address does not necessarily imply that it is disputed; it may simply lack identification. A personal note from a friend is typically a benign document without any intent to deceive. Therefore, the forged signature stands out as the only example that distinctly fits the definition of a questioned document due to the implications of forgery and deception.