The song `Amar Sonar Bangla`, which went on to become the National Anthem of Bangladesh, was indeed penned by Rabindranath Tagore, making option 4 the correct answer. This song stirred patriotic sentiments during the liberation struggle of Bangladesh.

To understand why the other options are incorrect:

Option 1, Rajni Kanta Sen, was a Bengali poet and lyricist known for his devotional compositions. But he is not the author of this patriotic song.

Option 2, Dwijendralal Ray, also a Bengali poet, playwright, and musician, was known for his contributions to Bengali literature. But, `Amar Sonar Bangla` was not among his works.

Option 3, Mukunda Das, was a poet and a prominent figure in the anti-British movement in Bengal. Although his works inspired independence movements, he did not write the Bangladeshi National Anthem.

So, despite their significant contributions to Bengali literature and independence movement, none of the authors in options 1-3 wrote `Amar Sonar Bangla`. That was the work of Rabindranath Tagore.