Option 1: a medieval treatise on music composed by Tansen - This option talks about a treatise on music composed by Tansen. However, the ‘Sur Sagar’ is not a treatise on music composed by Tansen. Therefore, this option is incorrect.
Option 2: a poetic work of Surdas - This option states that the ‘Sur Sagar’ is a poetic work of Surdas. Surdas was a 15th-century blind poet and singer, known for his devotional compositions in praise of Lord Krishna. The ‘Sur Sagar’ is indeed a poetic work written by Surdas. This option is correct.
Option 3: memories of Bahadur Shah Zafar - This option suggests that the ‘Sur Sagar’ is a collection of memories of Bahadur Shah Zafar. However, the ‘Sur Sagar’ is not associated with Bahadur Shah Zafar. Therefore, this option is incorrect.
Option 4: None of the above - This option implies that none of the previous options are correct. However, option 2, stating that the ‘Sur Sagar’ is a poetic work of Surdas, is correct. Therefore, this option is incorrect.
In conclusion, the correct answer is