What is the purpose of the video library? To help people improve their(_16_) abilities. 17. What problem may people have when using the library for the first time? They may have difficulty understanding(_17_). 18. What are people advised to do when listening to the video? Write down the(_18_) they hear and understand. 19. What should people do in listening to each conversation? Try to notice the (_19_). 20. How can people start watching their first video? All they need to do is to click on the link of(_20_).