Final answer:
In rational choice theory, skipping class with peers is an example of external influence because it involves peer pressure, which affects decision-making.
Step-by-step explanation:
In the context of rational choice theory, an external influence refers to factors outside an individual that impact their decision-making process. Among the provided scenarios, skipping class with peers is an example of an external influence (Option A), because it involves the social context and peer pressure, which can affect an individual's rational decisions. On the other hand, skipping class on one's birthday (Option B) can be considered an internal influence, premised on personal values or desires. Therefore, the correct answer to the question is A) Skipped class with peers.