There are three papers in the preliminary stage of the BPSC (Bihar Public Service Commission) exam. Let's discuss each paper in detail.

1. General Studies Paper I:
This paper tests the candidates' knowledge in various subjects such as history, geography, polity, economy, science, and current affairs. The key pointers of this paper include:

- History: Ancient, medieval, and modern history of India and Bihar.
- Geography: Physical, social, and economic geography of India and Bihar.
- Polity: Indian and Bihar governance, constitution, and political system.
- Economy: Basic concepts of economics, national income, poverty, and unemployment.
- Science: Physics, chemistry, biology, and technology-related topics.
- Current Affairs: National and international events, government schemes, awards, sports, etc.

2. General Studies Paper II:
This paper focuses on the logical reasoning and analytical abilities of the candidates. It consists of questions from the following areas:

- Comprehension: Reading and understanding passages followed by questions.
- Interpersonal skills: Communication, problem-solving, decision-making, etc.
- Logical reasoning and analytical ability: Deductive and inductive reasoning, analogies, syllogism, coding-decoding, etc.
- General mental ability: Numerical series, letter series, odd one out, relationship concepts, etc.

3. General Knowledge Paper:
This paper aims to assess the candidates' knowledge of current events and general awareness. The key pointers of this paper include:

- Indian and world history, geography, polity, and economy.
- Science and technology-related topics.
- Current affairs of national and international importance.
- Sports, awards, books, and authors.
- Indian culture, art, and heritage.
- Environment and ecology-related issues.

Each paper in the preliminary stage carries 150 marks, making a total of 450 marks. The duration of each paper is two hours. Candidates must score above the cutoff marks to qualify for the next stage of the BPSC exam.

In conclusion, the preliminary stage of the BPSC exam consists of three papers - General Studies Paper I, General Studies Paper II, and General Knowledge Paper. These papers assess the candidates' knowledge, logical reasoning, analytical abilities, and general awareness. It is essential for aspirants to thoroughly prepare for each subject to perform well in the exam.