第六課補充影片

https://www.youtube.com/watch?v=kzri5hlLm4o
https://www.youtube.com/watch?v=ZlD9ge7iOX0
https://www.youtube.com/watch?v=QVG9MiCSdsU
https://www.youtube.com/watch?v=VW-E3vjl9lk
https://www.youtube.com/watch?v=Wcv-Q1BP3XI&t=120s