The correct answer is option 2, Dinabandu Mitra. Neel Darpan is a famous drama that depicted the suffering of the indigo cultivators and the brutality of the planters. Dinabandu Mitra was the playwright who wrote this powerful drama.

Option 1, Harish Chandra Mukherjee, is incorrect. There is no known connection between him and the writing of Neel Darpan.

Option 3, Sisir Kumar Ghose, is also incorrect. Sisir Kumar Ghose was a prominent Bengali cinematographer and film director, but he did not write Neel Darpan.

Option 4, Ram Gopal Ghose, is also incorrect. There is no evidence to suggest that Ram Gopal Ghose wrote Neel Darpan.

It is important to note that the playwright Dinabandu Mitra wrote Neel Darpan, which shed light on the plight of the indigo cultivators and portrayed the cruelty of the planters.