Which of the following can be a defense against a libel suit?

Truth is considered an absolute defense against a libel suit because if the statement made can be proven true, it negates the claim of defamation. Libel involves making false statements that damage someone's reputation; therefore, demonstrating that the statements in question are factual eliminates the basis for the lawsuit. In the legal context of defamation, particularly in public relations, the burden of proof lies with the plaintiff to establish that the statements were not only false but also damaging to their reputation.

Other options, such as anonymity, popular opinion, and exaggeration, do not provide a solid legal defense against libel. Anonymity might protect the identity of the speaker but does not absolve them from the responsibility of what they say. Popular opinion does not equate to truth and does not shield someone from liability if the statement is false. Exaggeration might be seen in some contexts as a form of opinion or hyperbole, but it cannot serve as a defense if the statement is specifically harmful and can be determined to have been presented as fact. Hence, truth stands out as the most robust and recognized defense against a libel claim.