A person who commits a crime under immediate threat is acting under which defense?

The correct option in this scenario is duress. When a person commits a crime due to immediate threat or coercion from another party, they are considered to be acting under duress. This legal concept recognizes that individuals may be compelled to commit unlawful acts when faced with an imminent threat of harm or death to themselves or others. The key element of duress is the presence of a direct and immediate threat that leaves the individual with no reasonable alternative but to comply with the demands of the person exerting the threat.

In the context of the other options, necessity involves a situation where a person must commit a crime to prevent a greater harm from occurring, but does not necessarily involve a direct threat from another individual. Consent refers to the permission granted for something to happen, which is not applicable in this context. Self-defense relates to actions taken to protect oneself from imminent harm, but this does not fit the scenario where someone is coerced into committing a crime due to another person's threat. Therefore, the correct understanding of a person acting under immediate threat leads to the conclusion that they are under duress, which justifies the choice of option B.