Two statements are given, one is labelled as Assertion (A) and the other as Reason (R):
Assertion (A) The post-Independence Indian state was committed to the abolition of caste and explicitly wrote this into the Constitution.
Reason (R) The state was both unable and unwilling to push through radical reforms which would have undermined the economic basis for caste inequality.

Both (A) and (R) are true and (R) is not the correct explanation for (A)

The correct answer is Option 2: Both (A) and (R) are true and (R) is not the correct explanation for (A).

Assertion (A): "The post-Independence Indian state was committed to the abolition of caste and explicitly wrote this into the Constitution." — Correct. After Independence, the Constitution embodied the commitment to abolish caste-based discrimination by guaranteeing equality before the law, prohibiting discrimination on grounds of caste, and abolishing practices such as untouchability. 

Reason (R): "The state was both unable and unwilling to push through radical reforms which would have undermined the economic basis for caste inequality." — Correct. Although the state was committed to ending caste-based discrimination, it did not undertake sufficiently radical socio-economic reforms to completely dismantle the economic structures that sustained caste inequality. As a result, caste inequalities continued to persist in many spheres.

Why is (R) not the correct explanation for (A)? The Assertion describes the constitutional commitment of the state to abolish caste, whereas the Reason highlights the limitations in implementing deep structural reforms after Independence. The Reason does not explain why the state incorporated the abolition of caste into the Constitution; instead, it points to the gap between the state's constitutional commitment and its actual reform efforts.

NCERT: ... The dominant view in the nationalist movement was to treat caste as a social evil and as a colonial ploy to divide Indians. But the nationalist leaders, above all, Mahatma Gandhi, were able to simultaneously work for the upliftment of the lower castes, advocate the abolition of untouchability and other caste restrictions, and, at the same time, reassure the landowning upper castes that their interests, too, would be looked after. The post-Independence Indian state inherited and reflected these contradictions. On the one hand, the state was committed to the abolition of caste and explicitly wrote this into the Constitution. On the other hand, the state was both unable and unwilling to push through radical reforms which would have undermined the economic basis for caste inequality. At yet another level, the state assumed that if it operated in a caste-blind manner, this would automatically lead to the undermining of caste based privileges and the eventual abolition of the institution. For example, appointments to government jobs took no account of caste, thus leaving the well-educated upper castes and the ill-educated or often illiterate lower castes to compete on “equal” terms. The only exception to this was in the form of reservations for the Scheduled Castes and Scheduled Tribes."