Introduction:
The Union Public Service Commission (UPSC) is a constitutional body in India that is responsible for conducting various examinations and selecting candidates for civil services and other government posts. It was established under Article 315 of the Indian Constitution.

Explanation:
The correct answer to the question is option 'A', Article 315. Let's understand why.

Article 315:
Article 315 of the Indian Constitution deals with the establishment and composition of the Public Service Commission for the Union and the States. According to this article, there shall be a Public Service Commission for the Union and a separate Public Service Commission for each State. The Union Public Service Commission (UPSC) is responsible for conducting examinations and selecting candidates for various central government posts, while the State Public Service Commissions are responsible for conducting examinations and selecting candidates for state government posts.

Role of UPSC:
The UPSC is one of the most prestigious and important bodies in India. It plays a crucial role in the recruitment process of civil servants for the central government. The main functions of the UPSC include:

1. Conducting Examinations: The UPSC conducts various examinations such as the Civil Services Examination (CSE), Engineering Services Examination (ESE), Combined Defence Services Examination (CDSE), etc. These examinations are conducted to select candidates for different government services like Indian Administrative Service (IAS), Indian Foreign Service (IFS), Indian Police Service (IPS), etc.

2. Recruitment Process: The UPSC is responsible for formulating and implementing the recruitment process for various government posts. It issues notifications, conducts examinations, evaluates answer sheets, and interviews candidates for the selection process.

3. Appointment and Promotion: The UPSC also advises the President on matters related to the appointment, promotion, and disciplinary matters of civil servants. It ensures that the recruitment process is fair, transparent, and based on merit.

4. Advisory Role: The UPSC provides expert advice to the government on matters related to personnel management, training programs, and other administrative issues.

Conclusion:
In conclusion, the Union Public Service Commission (UPSC) of India has been established under Article 315 of the Indian Constitution. It is responsible for conducting examinations and selecting candidates for various central government posts. The UPSC plays a crucial role in the recruitment process of civil servants and ensures that the selection process is fair and based on merit.