The correct answer is option 'D': Charter Act of 1853.

The Charter Act of 1853, also known as the Government of India Act 1853, was an important legislative enactment passed by the British Parliament that had significant implications for the administration of British India. One of the key provisions of this act was the introduction of the Open Competition System for Indian Civil Services, which allowed Indians to participate in the civil service examinations.

The Open Competition System for Indian Civil Services was a groundbreaking step towards inclusivity and the empowerment of Indians in the British colonial administration. Prior to this act, the civil service was dominated by the British, and Indians were largely excluded from the higher administrative positions. The act aimed to rectify this imbalance by creating opportunities for talented Indians to join the civil services.

The act allowed Indians to compete on an equal footing with the British in the civil service examinations. It established the Civil Service Commission in London, which was responsible for conducting the examinations and selecting candidates based on their merit. Indians were now eligible to take these examinations and had the opportunity to secure high-ranking administrative positions in the British Indian government.

The introduction of the Open Competition System was a significant milestone in India's struggle for self-governance and representation. It provided a platform for Indians to demonstrate their abilities and compete with the British on an equal basis. This not only helped to break down barriers to Indian participation in the civil services but also paved the way for greater Indian involvement in the decision-making and administration of the country.

The Charter Act of 1853, with its provision for the Open Competition System for Indian Civil Services, marked a turning point in the history of Indian governance. It opened up opportunities for Indians to serve in the civil services, fostering a more inclusive and representative administration. The act laid the foundation for future reforms and eventually led to the Indian Civil Service being gradually Indianized in the following decades.