1. Why use bootstrap?
If you can point out browser support, mobile first, responsive layout, ease of writing, and consistent coding style , that's pretty much it.
2. What is the bootstrap grid system?
If you hear the word 12, it is over. If you can explain why it is 12 grids instead of 14 and 16 grids, it means that you have a deep understanding of the grid system.
3. Write a piece of inline, horizontal, vertical form code?
4. Write a responsive form code?
3, 4 mainly depends on the coding style including: proficiency, space indentation, DOM tag selection and other details.