2. The main learning task of a doctor is scientific research, so both interest and foundation are indispensable, otherwise it will be difficult to conduct in-depth research and publish papers with new ideas and viewpoints.

3. Most doctoral graduates enter colleges and universities to engage in teaching and scientific research, so no matter what their major is.

4. Generally speaking, interdisciplinary is not recommended. Unless you are particularly interested in related subjects and have a foundation, it is difficult to get into the exam. If you cross other majors, you often need to publish a paper to get the approval of your tutor.