Explanation:

- Public nuisance: This is a completed offense involving disturbance or harm to the public at large.

- Criminal attempt: This is an inchoate crime. It involves trying to commit a crime, even if the crime itself isn’t completed.

- Unlawful assembly: This is the gathering of people with the intent to commit an offense, but it's not considered an inchoate crime.

- Riot: This is a completed public disorder crime, which occurs when people act together violently.

Correct answer: Option 2, Criminal attempt