16.What is the purpose of the video library?To help people improve their___________________abilities.17.What problem may people have when using the library for the first time?They may have difficulty understanding__________________.18.What are people advised to do when listening to the video?Write down the__________________________they hear and understand.19.What should people do in listening to.each conversation?Try to notice the______________________________.20.How can people start watching their first video?All they need to do is to click on the link of_________________________