The correct answer is option 4: 3 only.

1. The first statement states that the Fundamental Duties can be enforced through writ jurisdiction. However, this is incorrect. Unlike the Fundamental Rights, the Fundamental Duties are not enforceable through writ jurisdiction. Writ jurisdiction is a legal mechanism used to enforce Fundamental Rights, but it cannot be used to enforce the Fundamental Duties.

2. The second statement states that the Fundamental Duties have formed a part of the Constitution since its adoption. This statement is correct. The Fundamental Duties were added to the Constitution through the 42nd Amendment Act, 1976. They were inserted after Part IV-A, which contains the Directive Principles of State Policy. Therefore, the Fundamental Duties have been a part of the Constitution since 1976.

3. The third statement states that the Fundamental Duties are applicable only to citizens of India. This statement is also correct. The Fundamental Duties, as mentioned in Article 51A of the Constitution, are applicable only to citizens of India. Non-citizens do not have Fundamental Duties.

In conclusion, the correct statements regarding the Fundamental Duties are statements 2 and 3. They have been a part of the Constitution since its adoption in 1976