Which of the following is a defense against insider dealing?

In the context of insider dealing, a crucial defense is the argument that the individual believed the information was widely disclosed. This perspective rests on the principle that if the information was already made public and is accessible to the general market, the individual cannot be said to have made use of non-public, sensitive information to gain an unfair advantage.

The rationale behind this defense is to establish that an individual reasonably perceived the information as public knowledge, thus negating the claim of insider trading. It emphasizes the importance of market transparency and the expectation that all investors should have equal access to pertinent information when making investment decisions.

The other options reflect situations that do not adequately address the core issue of insider trading. For instance, having no knowledge of the transaction does not inherently serve as a defense unless it can be proved that the person genuinely had no connection to the relevant information. Similarly, considering the information irrelevant or knowing the information has been leaked does not provide a solid legal argument against insider trading, as both circumstances may not absolve one of the duty to refrain from trading based on material non-public information.