As-if Natural experiments

Which of the following is an accurate description of an "as-if" natural experiment?

A political study where treatment assignment was determined by factors outside the control of the investigators. Assignment to the treatment was completely random.
A business experiment where assignment to treatment was determined by factors outside the control of the investigators. Assignment to the treatment was not literally random, but it was unrelated to variables that affect the outcome.
A psychology study conducted in a naturalistic setting by investigators. Assignment to the treatment was completely random.
A zoological experiment conducted in a naturalistic setting by investigators. Treatment assignment was not literally random, but it was unrelated to variables that affect the outcome.