Subject requirements for each BPSC exam vacancy vary depending on the nature of the vacancy and the specific job role. BPSC (Bihar Public Service Commission) conducts various exams for different positions in the state government. Here are some of the common subject requirements for BPSC exam vacancies:

1. Administrative Services:
- General Studies: This subject covers a wide range of topics including Indian history, geography, polity, economy, science and technology, current affairs, and environment.
- General Hindi: Candidates need to have a good understanding of Hindi grammar, vocabulary, comprehension, and writing skills.
- General English: Candidates need to have a good command of English grammar, vocabulary, comprehension, and writing skills.

2. Police Services:
- General Studies: Similar to the administrative services, candidates need to have a strong knowledge of Indian history, geography, polity, economy, science and technology, current affairs, and environment.
- General Hindi: Same as above.
- General English: Same as above.

3. Judicial Services:
- Law: Candidates need to have a thorough understanding of various legal subjects such as Constitution of India, Indian Penal Code, Code of Criminal Procedure, Code of Civil Procedure, Evidence Act, etc.

4. Engineering Services:
- Civil Engineering: Candidates need to have a strong knowledge of various civil engineering subjects such as structural analysis, geotechnical engineering, water resources engineering, transportation engineering, etc.
- Mechanical Engineering: Candidates need to have a strong knowledge of various mechanical engineering subjects such as thermodynamics, fluid mechanics, manufacturing processes, machine design, etc.
- Electrical Engineering: Candidates need to have a strong knowledge of various electrical engineering subjects such as electrical circuits, power systems, control systems, electrical machines, etc.

5. Medical Services:
- Medical Science: Candidates need to have a strong knowledge of medical subjects such as anatomy, physiology, pharmacology, pathology, microbiology, etc.

It is important for candidates to thoroughly go through the official notification of each BPSC exam vacancy to understand the specific subject requirements. The syllabus and subject requirements may vary for different positions and exams. Candidates should also refer to previous years' question papers and study materials to prepare effectively for the exams.