If A attempts to slap B, is B justified in using lethal force to prevent it?

The rationale for the option that asserts it is not justified for B to use lethal force in response to A attempting to slap him is grounded in the principle of proportionality in self-defense. The law typically recognizes that a person is allowed to use reasonable force to protect themselves from an imminent threat. However, the level of force used in self-defense must be proportionate to the threat faced.

In this scenario, A's attempt to slap B represents an aggressive but minor physical threat. Slapping does not constitute a level of violence that would warrant a lethal response. The law seeks to prevent excessive measures in self-defense, which would include the use of lethal force against a non-lethal threat.

Therefore, the appropriate response for B would be to defend himself using reasonable measures that correspond to the threat, such as blocking the slap or stepping away, instead of resorting to lethal force. This aligns with the legal standard that allows self-defense only when the use of force is necessary and proportional to the threat posed.