Final answer:
The correct answer is a) Ex post facto law. An ex post facto law retroactively criminalizes an act after it was committed. It is prohibited by the Constitution to prevent individuals from being punished for acts that were legal at the time.
Step-by-step explanation:
The correct answer to the question is a) Ex post facto law.
An ex post facto law is a law that retroactively criminalizes an act after it was committed. It is prohibited by the Constitution to prevent individuals from being punished for acts that were legal at the time they were committed. For example, if you did something 10 years ago that was legal, but the law was changed today to make it illegal, you cannot get into trouble for it.
This protection guarantees that individuals are warned ahead of time that their actions are illegal and prevents unfair punishment.