The correct answer is option 'A', which states that the 25th Amendment Act (1971) introduced Article 31C to protect a law seeking to implement a directive under 39 (b)-(c) from being declared ultra vires on the ground of contravening.

Explanation:
The 25th Amendment Act of 1971 was brought in to amend various provisions of the Constitution of India. One of the significant changes made by this amendment was the introduction of Article 31C.

Article 31C was added to the Constitution to protect laws that sought to implement the directive principles of state policy contained in Article 39(b) and (c) from being declared ultra vires on the ground of contravening the fundamental rights guaranteed under Articles 14, 19, and 31.

Let's break down the explanation further:

1. Introduction of Article 31C:
- The 25th Amendment Act introduced Article 31C into the Constitution of India.
- Article 31C is a constitutional provision that provides protection to laws aimed at implementing the directive principles of state policy.

2. Purpose of Article 31C:
- Article 31C was incorporated to ensure that laws made to implement the directive principles of state policy are not invalidated by the courts on the grounds of violating fundamental rights.
- The directive principles of state policy, enshrined in Part IV of the Constitution, are non-justiciable in nature. However, Article 31C was introduced to give them more teeth by providing immunity to laws enacted for their implementation.

3. Protection from Ultra Vires:
- Ultra vires means an act that is beyond the legal power or authority of the entity performing it.
- Article 31C protects laws that seek to implement the directive principles from being declared ultra vires on the grounds of contravening fundamental rights.
- This means that even if a law made to implement directive principles potentially violates fundamental rights, it cannot be struck down by the courts.

4. Grounds of Contravening:
- The grounds of contravening refer to the violation of fundamental rights guaranteed under Articles 14, 19, and 31 of the Indian Constitution.
- Article 14 ensures the right to equality, Article 19 guarantees certain fundamental freedoms, and Article 31 safeguards the right to property.
- Article 31C provides protection to laws implementing directive principles from being invalidated on the basis of contravening these fundamental rights.

In conclusion, the 25th Amendment Act (1971) introduced Article 31C into the Constitution of India to protect laws aimed at implementing the directive principles of state policy from being declared ultra vires on the grounds of contravening fundamental rights.