The English Language continued to be used for official purpose of the Union via section 3 of the Official Language Act which came into force in the year:

Correct option is A

Correct Answer Option (a): 1963
Explanation:
The Official Language Act, 1963 was enacted to ensure the continued use of the English language for official purposes of the Union of India along with Hindi, even after the 15-year period stipulated by the Constitution had ended.

Information Booster:

Constitutional Background:
The Indian Constitution (Article 343) originally stipulated that Hindi in the Devanagari script would replace English as the official language of the Union within 15 years of the Constitution coming into effect (i.e., by January 26, 1965).
However, concerns arose, especially from non-Hindi-speaking states, about the imposition of Hindi.

Official Languages Act, 1963:
To address these concerns, the act was passed, allowing English to continue as an additional official language along with Hindi after 1965.
This ensured the smooth functioning of the Union and upheld the linguistic diversity of India.