Answer:
The semantic problem you experienced was due to B. relative language.
Step-by-step explanation:
Relative words gain their meaning by comparison. That means when someone uses relative language, what they are saying can mean something different when compared to what their interlocutor understood. For instance, when a friend says she'll call me back soon, I'll interpret the word "soon" according to my own standards. To me, "soon" means in a few minutes, but to her it may mean in a couple of hours.
In the situation described in the passage, the two friends had different comprehensions of what "good chance" meant when compared to each other. That is why one of them was disappointed when the other didn't show up. For that friend, "good chance" mean a high probability, while for the other it didn't.