Explanation:

Dr. Mahabub-ul-Haq, a Pakistani economist, is widely credited with introducing the concept of human development and pioneering the Human Development Index (HDI) in the early 1990s. He emphasized that development should be about enlarging people's choices, not just economic growth. Option A, Prof. Amartya Sen, an Indian Nobel laureate, significantly contributed to the theoretical framework of human development with his 'capabilities approach,' which complements Mahabub-ul-Haq's work but did not introduce the concept. Options C, Ellin C. Semple, and D, Ratzel, were prominent geographers associated with environmental determinism and human geography, not the concept of human development.