课程与学业话题对话理解 — 英语填空题
题目
听录音，补全对话中缺失的关键信息。
M: Hi, what are you doing here?
W: I'm trying to ___ a course online.
M: Which one?
W: Introduction to Computer Science. It's very popular.
M: Is it full?
W: No, there are still a few ___ left.
M: Do you have to pay?
W: No, it's ___.