Which defense can be used if the pressure is applied by a person with reasonable firmness inability to resist?

The correct answer is compulsion. In legal terms, compulsion refers to a situation where an individual is forced to take an action against their will due to the pressure exerted by another person. This pressure must be significant enough to impair the individual's ability to resist or make a voluntary choice. Compulsion highlights the lack of genuine consent and emphasizes the inability to act freely due to the overwhelming influence or threat posed by another person.

In this context, duress often refers to similar scenarios where an individual is coerced into acting in a certain way, but it typically involves threats of harm or actual physical violence. The nuance between compulsion and duress can sometimes lead to confusion.

Intoxication refers to impairment caused by drugs or alcohol, which affects a person's ability to make rational decisions but does not necessarily involve external pressure from another individual. Entrapment occurs when law enforcement induces a person to commit a crime that they would not have otherwise committed, which is unrelated to the scenario described in this question.

Thus, compulsion aligns with the given parameters of the question regarding pressure applied by another person that specifically inhibits the ability to resist.