Most students should not need to take this exam. There are several common situations:
1. I want to apply for GRE sub-score in the name of the school department (required exam), which is naturally required (strongly recommended or considered).
2. Subjects that must be tested in the sub (see article 1) or those related to cross-disciplines are generally also tested.
3. The GPA of sub-exam-related subjects is not very good, and I want to make up for it through sub's scores. In this case, you can take the exam or not. It can't be said that it doesn't work at all, but it is very small. With this time, it is better to work harder in other aspects.
4. I didn't do well in the math part of 4.GRE, and I want to make up for it with math sub. In this case, don't take the exam. Mathematics sub and GRE mathematics examination contents are completely different and cannot be compensated.
About the content of the exam:
Examination time 170 minutes, all majors are the same. The number of questions in each major is different, but they are all single-choice questions with 5 options for each question.
See the exam outline for details:
Mathematics, chemistry, biology, biochemistry, physics, psychology, computer, literature.