The correct option is 2 and 3 only.
Explanation
Nandalal Bose was a pioneer of modern Indian art and a leading figure of the Bengal School of Art. His work was deeply intertwined with the Indian freedom struggle and the Swadeshi movement, reflecting nationalist sentiments through indigenous styles and themes.
Statement 1 is Incorrect: Nandalal Bose did not design the official flag of the British Indian Army. He is, however, famous for designing the "Haripura Posters" for the 1938 Indian National Congress session at the request of Mahatma Gandhi. Additionally, he designed the emblems for the Bharat Ratna and Padma Shri awards in independent India.
Statement 2 is Correct: Nandalal Bose illustrated the Bengali primer Sahaj Path, written by Rabindranath Tagore. He used woodcuts and linocuts to create simple, educational illustrations that facilitated the teaching of the Bengali language and new ideas to children.
Statement 3 is Correct: Nandalal Bose, along with his students from Kala Bhavana (Santiniketan), was entrusted with the task of illuminating and decorating the original manuscript of the Constitution of India. The artwork in the Constitution depicts various phases of Indian history, from the Mohenjodaro period to the freedom struggle.
Key Takeaway: Nandalal Bose is best known for illustrating the original manuscript of the Constitution of India, creating the Haripura Congress posters, and illustrating Rabindranath Tagore's Sahaj Path.