Answer:
1. External Style Sheets are useful as it keeps the style and content separately and doesn’t allow it to mix with each other. It can control the styles for multiple documents, whereas inline style mixes the content with the style and make the code messier.
2. External style sheet allows the creation of various classes in a structured way, whereas inline style sheet can’t create or control class elements.
3. External style sheet can use selector and grouping methods to apply styles, whereas inline styles can’t use selector and grouping methods.
