Answer:
the foot-in-the-door phenomenon.
Explanation:
From the given question, someone is trying to convince his parents to send him to Europe. First, he asks them for a small favor (a bus ticket to a local city), hoping that later they will be more willing to send you on the longer trip. This technique is known as foot-in-the-door technique.
This technique is used as a compliance tactic to get what a person wants by asking for small favors so that a larger request would be granted.
